Pigments and Color Temperature
Warm and Cool
You likely can see that some colors are warmer than others. For example, most can see that red is warmer than purple, and purple is warmer than blue. One fact about pigments that one may not have considered is that some reds are warmer than others and some blues are cooler than others. In the image below there are four pairs of pigments: two reds, two yellows, two greens, and two blues.
Look carefully at the colors. Can you see that alizarin crimson is cooler than cadmium red? Lemon yellow is cooler than cadmium yellow. Sap green is warmer than viridian green. Phthalo blue is warmer than ultramarine blue. But why does any of this matter? It matters for at least two reasons: Color mixing and rendering form, space, and light.
Temperature and Color Mixing
If you do not have a tube of green paint, and want to mix up a green on your palette with some blue and some yellow this information is useful. For example, if you want to mix a higher intensity (higher chroma) green, which yellow and which blue should you use? It does matter. A cooler yellow, the yellow that leans towards blue will when mixed with a blue make a more saturated green, whereas a wamer yellow (cadmium yellow) mixed with a blue will create a less vibrant green because cadmium yellow has a bit of red in it (and remember, red and green are complements and when mixed they create a neutral). So cadmium yellow used in making a green results in a lower chroma green or a pre-neutralized green. At times, one wants a more neutral green, so this can be useful as well.
Temperature and Rendering Form, Space, and Light
Shadows tend to be cooler than areas in the light. Cool colors tend to recede and warm colors often come forward. Color temperature can be used to more effectively render light and create the illusion of form. For example, imagine that you are painting a picture of a blue box sitting on a table. The box is illuminated by an incandescent light. The sides of the box lit by the light will be a lighter blue, but they will also be a warmer blue. The shadow side of the box will be darker, likely a lower chroma blue and also a cooler blue. Paying attention to color temperature can allow a painter to more accurately render light, form, and space. Along these lines, the Impressionists often used blue for shadows and added yellow into their subjects illuminated by daylight.
Temperature and Harmonies
When organizing forms in a picture via color, tempurature can affect color harmonies. Consider how closely a lemon yellow coordinates with a green and a blue. Lemon yellow is a cooler yellow and will be more closely aligned with blues and greens than a cadmium yellow. Consider green, red, and blue pairings with each of their respective analogous colors.
updated April 2, 2021