Many artists don't really think much beyond the basics of the color wheel. Warm colors are red, yellow, orange, etc. cool colors are blues, greens and violets, but are they really? If you place a little bit of violet next to yellow-orange, especially red-violet, you get a warm blue violet. Green is an enigma as well, a bit of blue-green next to blue-violet becomes cool yet put it next to the pink of the sky and it becomes warm.
Painting the color of light at different times of the day has challenged artists from Sorolla to present day. Light changes temperature at different times of the day and in different weather conditions. Cloudy days cool the light and warm the shadows while sunny days warm the light and cool the shadows.
The changes are subtle, and you really have to train your eyes to pick them up. Plein air painting forces you to study the light and the qualities of light at different times in order to truly capture the light.
Thomas Jefferson Kitts, in an excellent blog post on his website describes this phenomenon very eloquently:
"...in a nutshell, on an overcast day the primary light (from the sun positioned above the clouds) is filtered and turns cooler by the time it reaches the ground. (Think of that layer of clouds being an extreme form of atmospheric perspective. More of the yellow and red part of the spectrum is being being filtered by the clouds.) As a result, on the ground we 'perceive' cool lights and warm shadows. The opposite of what we have been discussing in this post. Overcast light is actually more complicated to explain than the more straight-forward sunlight/skylight thing, so I will save the cool/warm thing for another day."
I tend to focus more on value, then secondarily on color and color temperature. Other painters, including the Impressionists, many modernists, and well-respected contemporary painters focus more on color temperature first and place small blotches of color next to each other to describe light.
Beautiful paintings tend to have a balance of warm and cool, but pushing the temperature to the warms with more yellows and oranges, yellow-green and reds, will give the impression of strong, warm afternoon light. Pushing the cools with blue-greens, blues, and blue violets, will give the impression of early morning light, or evening shadows.
Want to try this on your own? Set up a still life study in natural light. Practice making simple shapes with values and push the color temperature to warm up the lights with some yellows, and cool off the darks with some blues. Notice how the color reflects, not just sky color, but color from the table cloth, items on the table, your still life objects reflect off of each other. Play with the quality of light, adding warms and cools where appropriate.
Please post what you make and share!