Author: PIW Site Owner

Cobalt Blue is one of the most balanced and reliable blues in watercolor. Neither overly warm nor aggressively cool, it occupies a unique middle ground that makes it indispensable for glazing, atmospheric work, and subtle color relationships.

Understanding Cobalt Blue on the Palette

Cobalt Blue is a pure transparent color that is considered to be a neutral blue. It is the BLUE used for the layered wash – glazing watercolor technique. For the PRIMARY BLUE in color schemes based on Stephen Quiller’s “Quiller Color Wheel” and his book “Color Choices: Making Color Sense Out of Color Theory“, see Winsor Blue (Green Shade).

Cobalt Blue’s neutrality allows it to function as a stabilizing force on the palette. Rather than pushing mixtures strongly warm or cool, it supports harmony, softness, and controlled value development—especially important in layered watercolor techniques.

Pigment Information: What Makes Cobalt Blue Unique

True Cobalt Blue is made from Cobalt Aluminate (PB28), a historic pigment introduced in the early 19th century and still widely respected today.

Key characteristics of Cobalt Blue (PB28):

• Excellent lightfastness
• Moderate transparency
• Medium tinting strength
• Subtle natural granulation

Because it is cobalt-based, Cobalt Blue tends to be more expensive than modern synthetic blues, but it offers handling qualities that many artists find irreplaceable.

Why Cobalt Blue Is Ideal for Glazing

Cobalt Blue is especially valued for layered wash (glazing) techniques because it:

• Builds color gradually without overwhelming lower layers
• Maintains clarity when applied in multiple transparent washes
• Creates soft transitions rather than hard-edged saturation

This makes it particularly effective for skies, water, atmospheric distance, and shadow development.

Handling Characteristics & Surface Behavior

Cobalt Blue is known for:

• Gentle granulation that adds texture without distraction
• Predictable flow in wet washes
• A soft, slightly muted appearance compared to Phthalo or Ultramarine Blues

On textured papers, its granulation can enhance skies and natural surfaces. On smoother papers, it remains calm and even, making it versatile across styles.

Cobalt Blue vs. Other Common Blues

Understanding how Cobalt Blue differs from similar blues helps with intentional palette choices:

• Cobalt Blue: neutral, granulating, excellent for glazing and atmosphere
• French Ultramarine Blue: warmer, more granulating, stronger mixing power
• Winsor Blue (Green Shade): cool, intense, staining, high tinting strength

Cobalt Blue excels where subtlety and control are more important than intensity.

Mixing Behavior & Color Theory Applications

While not typically used as a primary blue in color-wheel systems, Cobalt Blue:

• Produces gentle, natural greens when mixed with cool yellows
• Creates soft violets with reds without overpowering them
• Helps neutralize warm passages without darkening excessively

Its restrained nature makes it ideal for nuanced color development rather than bold chromatic statements.

Best Uses for Cobalt Blue

Ideal Applications

• Skies and clouds
• Water and reflections
• Atmospheric perspective
• Glazing and layered washes
• Cooling warm passages

Cobalt Blue is especially effective in paintings where light, air, and depth are central themes.

Limitations of Cobalt Blue

Despite its strengths, Cobalt Blue has some limitations:

• Lower chroma than modern synthetic blues
• More expensive due to cobalt content
• Less suitable for high-impact, saturated color passages

For intense color schemes or strong primary mixing, a different blue may be more appropriate.

A Note on Cobalt Blue’s Role on the Palette

Cobalt Blue is a “supporting” blue, not a dominating one. Its value lies in restraint, balance, and subtlety. For artists who rely on glazing, atmospheric depth, and controlled color transitions, Cobalt Blue remains an essential and time-tested watercolor pigment.

Hooker’s Green is a classic, practical watercolor green that has long been associated with landscape painting. Unlike single-pigment greens, it is typically a convenience mixture, designed to produce natural-looking foliage colors straight from the palette.

Understanding Hooker’s Green on the Palette

Hooker’s Green is a more neutralized color than the pure transparent Viridian. So, I have not included it in my color schemes. It is a warm green useful in mixing a variety of greens for expressing landscapes and receding planes.

Because Hooker’s Green is already moderated, it behaves differently than pure greens on the color wheel. Rather than acting as a structural color for theory studies, it functions best as a practical mixing green—one that helps artists quickly arrive at believable natural color.

Pigment Information: Why Hooker’s Green Is a Convenience Color

Hooker’s Green is not a single pigment. Instead, it is typically a blend of blue and yellow pigments, sometimes with a red or earth color added to neutralize the mixture.

Common pigment combinations may include:

• Phthalo Green (PG7 or PG36)
• Phthalo Blue (PB15)
• Yellow pigments (PY110, PY150, or similar)
• Occasionally earth pigments for warmth

Because formulations vary by manufacturer, Hooker’s Green can differ noticeably in:

• Temperature (yellow-leaning vs. blue-leaning)
• Transparency
• Granulation
• Tinting strength

This makes brand choice especially important.

Historical Context: Where Hooker’s Green Comes From

Hooker’s Green is named after William Hooker, a 19th-century botanical illustrator who reportedly mixed his own greens to achieve realistic plant colors. Paint manufacturers later adopted the name to describe premixed greens designed for botanical and landscape work.

This historical association explains why Hooker’s Green remains popular among:

• Landscape painters
• Botanical illustrators
• Artists working in naturalistic color ranges

Handling Characteristics & Mixing Behavior

Hooker’s Green is valued for its:

• Ready-made natural appearance
• Moderate tinting strength
• Ease of modification

Because it is already neutralized, Hooker’s Green:

• Dulls quickly when mixed with complements
• Responds well to temperature shifts rather than heavy neutralization
• Benefits from being adjusted with yellows, blues, or earth tones

It is especially effective when you want to suggest complexity without overmixing.

How Hooker’s Green Differs from Viridian and Phthalo Green

Understanding these distinctions helps artists choose intentionally:

• Viridian: cool, granulating, single-pigment, excellent for color theory
• Phthalo Green: intense, staining, high-chroma, very powerful
• Hooker’s Green: mixed, moderated, natural-looking, landscape-friendly

Hooker’s Green sacrifices purity for practicality—and that is precisely its strength.

Best Uses for Hooker’s Green

Ideal Applications

• Foliage and trees
• Middle-ground and background landscapes
• Receding planes
• Woodland scenes
• Botanical studies requiring natural greens

Hooker’s Green excels when realism and atmosphere matter more than chroma.

Limitations of Hooker’s Green

While useful, Hooker’s Green is not ideal for every situation:

• Not suitable for structured color wheel studies
• Less predictable due to multi-pigment composition
• Can become muddy if overmixed
• Not ideal for high-chroma or abstract color work

For these reasons, it is best treated as a supporting color, not a foundational one.

How to Modify Hooker’s Green Effectively

To extend its usefulness:

• Add yellow to bring foliage forward
• Add blue to cool and deepen distant greens
• Add earth colors (Burnt Sienna, Raw Umber) for shadowed passages
• Add red or violet sparingly to neutralize without killing the color

Small adjustments go a long way.

A Note on Hooker’s Green’s Role on the Palette

Hooker’s Green is not meant to replace intentional mixing—it complements it. When used thoughtfully, it speeds up workflow, supports natural color, and helps establish believable depth in landscape painting.

For artists focused on expressive realism and atmospheric space, Hooker’s Green remains a valuable and time-tested watercolor choice.

Viridian is a distinctive and often misunderstood green in watercolor. Known for its cool temperature and subtle granulation, it plays a vital role in balanced palettes—especially for artists who value atmospheric color, natural mixtures, and thoughtful color theory.

Why Viridian Works as a Secondary Green

I use Viridian as the SECONDARY GREEN on the color wheel because it is a pure transparent color that is perfect for its complementary color listed below. Its cool, blue-leaning character allows it to interact cleanly with reds and violets, producing a wide range of muted neutrals and shadow colors without overpowering a mixture.

Viridian’s relatively low tinting strength makes it ideal for controlled mixing and layered washes. Rather than dominating a mixture, it allows other pigments to participate—an important quality when studying color relationships or working within a limited palette.

Pigment Information: Genuine Viridian vs. Viridian Hue

True Viridian is made from Hydrated Chromium Oxide (PG18), a historic pigment introduced in the 19th century as an alternative to the less stable Emerald Green.

Key characteristics of genuine Viridian (PG18):

• Excellent lightfastness
• Cool, slightly bluish green
• Moderate transparency
• Natural granulation in washes

Because PG18 is relatively weak in tinting strength and slower to rewet, many manufacturers also offer Viridian Hue, which is often formulated with Phthalo Green (PG7 or PG36), a transparent STAINING pigment, and other pigments to increase chroma and flow.

While Viridian Hue can appear brighter and more staining, it does not behave the same way in mixtures. Artists who prioritize subtlety, granulation, and historical handling often prefer genuine Viridian.

Handling Characteristics & Surface Behavior

Viridian is known for:

• Soft granulation, especially visible in textured paper
• A slightly chalky appearance when used thickly
• Gentle diffusion in wet washes

These properties make it particularly effective for:

• Water
• Atmospheric distance
• Shadowed foliage
• Cooling down warm passages without darkening them excessively

Viridian also lifts more easily than staining greens, which is helpful in watercolor corrections and light adjustments.

Why Viridian Excels in Color Theory Studies

Viridian is especially valuable in structured color systems because it:

• Mixes beautifully with reds to create natural neutrals
• Avoids harsh blackening when paired with its complement
• Maintains harmony in secondary and tertiary mixtures

Its restraint makes it an ideal teaching pigment for understanding balance, temperature shifts, and value control.

Color Schemes Using Viridian

The following color schemes are based on Stephen Quiller’s “Quiller Color Wheel” and his book “Color Choices: Making Color Sense Out of Color Theory.“

Complementary

The complementary color sits on the opposite side of the color wheel. For Viridian, the complementary color is:

• Permanent Rose or Alizarin Crimson

This pairing produces a wide range of muted violets, browns, and near-neutrals—excellent for shadows, bark, and subdued passages.

Split-Complementary

The split-complementary colors are the two colors located on either side of the complementary color on the color wheel. The following are the split-complementary colors for Viridian:

• Winsor Violet
• Cadmium Red Deep

This scheme allows for expressive variation while maintaining balance and avoiding overly harsh contrasts.

Analogous

Going clockwise on the color wheel from GREEN to BLUE, the analogous colors for Viridian are:

• Manganese Blue Hue
• Winsor Blue (Green Shade)

These combinations are especially effective for water, sky reflections, and cool atmospheric transitions.

Triadic

This Triadic consists of three SECONDARY colors. In addition to Viridian, the other colors that make up this Triadic color scheme are:

• Permanent Mauve
• Cadmium Scarlet

This triad offers a sophisticated balance of cool and warm notes, ideal for expressive yet harmonious compositions.

Viridian vs. Phthalo Greens: A Practical Comparison

Viridian is often compared to Phthalo Green, but their behavior differs significantly:

• Viridian: softer, granulating, lower tinting strength, easier to control
• Phthalo Green: intense, staining, high-chroma, easily overpowering

Viridian excels when subtlety and atmosphere are more important than saturation.

When Viridian Shines—and When It Doesn’t

Best Uses

• Water and reflections
• Distant foliage
• Cooling warm passages
• Shadow neutrals
• Classical and limited palettes

Limitations

• Not ideal for bright spring greens without modification
• Can appear dull if overused alone
• Requires mixing to achieve high-chroma greens

A Note on Viridian’s Place on the Palette

Viridian is not a shortcut green—it is a “thinking” green. Its strength lies in restraint, balance, and interaction with other colors. For artists focused on color harmony, atmospheric depth, and intentional mixing, Viridian remains an essential and irreplaceable pigment on the watercolor palette.

Aureolin is one of those watercolor colors that rewards subtlety and intention. While it may not be the brightest yellow on the palette, it plays a crucial role in transparent watercolor painting—especially when color harmony and clean mixing matter.

Why Aureolin Works as a Primary Yellow

I use Aureolin as the PRIMARY YELLOW on the color wheel because it is transparent. Its cool temperature and clarity allow it to mix cleanly with both blues and reds, producing secondary and tertiary colors that remain luminous rather than muddy. This makes it especially well-suited for color theory studies, glazing, and layered watercolor techniques.

Aureolin’s lower tinting strength encourages controlled mixing and gradual color shifts, which is ideal for artists who want subtlety rather than overpowering saturation.

It can be substituted with Cadmium Lemon, which is semi-opaque. While Cadmium Lemon offers stronger coverage and higher tinting strength, it behaves very differently in mixes and glazes. Understanding the distinction between transparency and opacity is essential when choosing a primary yellow.

Pigment Information: True Aureolin vs. Aureolin Hue

Traditional Aureolin is made from Potassium Cobaltinitrite (PY40), a cobalt-based pigment introduced in the 19th century. Historically, it was prized as one of the first transparent cool yellows available to watercolorists.

However, true Aureolin (PY40) has some important characteristics to be aware of:

• Moderate lightfastness, particularly in diluted washes
• Relatively low chroma and tinting strength
• Higher cost due to its cobalt content

Because of these limitations, many modern paint manufacturers now offer Aureolin Hue, using alternative yellow pigments that are more lightfast and environmentally safer. While these hues may not behave exactly like PY40, they are often preferred for archival and professional work.

Some artists continue to use genuine Aureolin for its unique handling and historical qualities, while others opt for modern substitutes for longevity.

Why Aureolin Excels in Color Theory Studies

Aureolin is particularly effective in structured color systems because it:

• Produces natural, believable greens when mixed with blues
• Creates soft, luminous neutrals when paired with its complement
• Maintains clarity in layered washes due to its transparency

These qualities make it an excellent choice for learning and applying color relationships in a controlled way.

Color Schemes Using Aureolin

The following color schemes are based on Stephen Quiller’s “Quiller Color Wheel” and his book “Color Choices: Making Color Sense Out of Color Theory.“

Complementary

The complementary color sits on the opposite side of the color wheel. For Aureolin, the complementary color is:

• Permanent Mauve

When mixed, these two colors create soft neutrals that are ideal for shadows and subdued passages.

Split-Complementary

The split-complementary colors are the two colors located on either side of the complementary color on the color wheel. The following are the split-complementary colors for Aureolin:

• Ultramarine Violet
• Winsor Violet

This scheme allows for greater variety while maintaining harmony, especially useful in expressive or layered compositions.

Analogous

Going clockwise on the color wheel from YELLOW to GREEN the analogous colors for Aureolin are:

• Winsor Green (Yellow Shade)
• Viridian

These combinations are excellent for foliage, light-filled landscapes, and atmospheric transitions.

Triadic

The three PRIMARY colors on the color wheel are YELLOW, BLUE and RED. In addition to Aureolin, the other colors that make up this Triadic color scheme are:

• Winsor Blue (Green Shade)
• Alizarin Crimson

This triad offers a wide mixing range while remaining balanced and harmonious.

Aureolin vs. Cadmium Lemon: When to Substitute

While Cadmium Lemon can substitute for Aureolin on the color wheel, the results will differ:

• Aureolin: transparent, subtle, ideal for glazing and delicate mixtures
• Cadmium Lemon: semi-opaque, stronger, more assertive in mixes

Opacity affects how colors interact, particularly in complementary and triadic schemes, so substitutions should be made with intention.

When Aureolin Shines—and When It Doesn’t

Best Uses

• Atmospheric landscapes
• Sunlit foliage
• Skin undertones
• Classical or restrained palettes
• Glazing and underpainting

Limitations

• Not ideal for high-chroma florals
• Can feel weak in bold, graphic applications
• Not the most archival yellow for exhibition work if using true PY40

A Note on Aureolin’s Place on the Palette

Aureolin may not be the brightest or strongest yellow available, but its transparency, cool temperature, and mixing behavior make it an exceptional choice for color theory studies and controlled, luminous watercolor work. When used intentionally, it supports harmony, light, and subtlety—qualities at the heart of watercolor painting.