Monday Morning Art School: what is color?

the unique way in which the cone cells in the human eye are stimulated by electromagnetic radiation. How an object reflects or emits light gives it its unique color.

In common parlance, we think of red, green or blue as colors. In art, however, those aren’t colors. Colors have three attributes, all of which you must understand in order to navigate color space successfully:

Value – How light or dark is the pigment?

Hue – Where does the color sit on the color wheel? All colors fall into one of the following hue families: red, orange, yellow, green, blue and violet. Within those families, however, are many subdivisions.

Chroma – How much intensity, or “punch” does the color have?

Since color has three attributes, it exists in a three-dimensional color space. However, we’re used to looking at it in two dimensions, in the form of a color wheel. I think the Quiller watercolor wheel is the best color wheel, since it shows you where neutral pigments fall inside the hue families.

Still, the conventional color wheel doesn’t take value into consideration. Every pigment has its own natural darkness or lightness. Dioxazine purple, for example, is very dark coming out of the tube. Lemon yellow is very light coming out of the tube. That does not mean that dark colors are cool and light colors are warm, however. Consider burnt umber. It’s very dark, and it’s also very warm.

There’s a misunderstanding that mixing across the color wheel darkens pigments. Only with certain greens and reds does this work. Mixing across the color wheel gives you neutrals: grays and browns.

We call the hue families of green, blue and violet “cool” and the hue families of yellow, orange and red “warm.” Within each hue family, there are warm and cool variations. Gamblin has this nifty chart of warm and cool pigments so you can see where your paints fall.

White, black, and grey are chromatic neutrals. Raw umber is fairly neutral. Naphthol red and phthalo blue are very high-chroma colors. In general, modern pigments are much more intense than the mineral pigments of the Renaissance.

It works to sort colors this way. I use a system of paired primaries which gives me a great, high-key mixing range. However, the whole idea of warm-vs.-cool is a painterly convention. It’s best to not have this discussion with a physicist, who will tell you that you have it backwards. He may be right, but that doesn’t mean he can paint.

I’ve written about the color temperature of light here, but there’s a simple rule that helps. The predominant shadows will always be the opposite (across the color wheel) from the color of the light. On a sunny day, the light will be cool and the shadows will be warm. At dusk the light will be golden and the shadows violet. Of course, there are exceptions to this rule, but it’s a good place to start.

I strongly recommend this video from Gamblin, which organizes color space in three dimensions. It’s also full of information about the history of color.