After having just given a talk on understanding color and how to use it, I've decided to post a few of the concepts here on the blog. Especially since I haven't been as diligent about posting as I would like. I'll talk generally at first, and in later posts I'll cover some more specific ideas about color. I'm assuming that you know the basics of a color wheel, and will move on beyond that so as not to get lost in the quagmire of abstract color theory, but use it for more practical purposes.
One of the most important concepts of color is understanding and using color temperature schemes. When picking an overall color for your painting think about what mood you want to evoke, as this will make the choosing of colors easier.
Cool colors are commonly viewed as calmer and more relaxing as well as being cold. Warm colors are usually associated with energy and movement and heat. Above is an extreme example of that idea in nature. One can feel the coldness of the iceberg above, but also the quiet, peaceful solitude, barely a bird around. With the lava, the tension builds quickly. The heat is strong and the energy is fast moving. We can hear the crackle and pop of the fire. These qualities can be used in paintings as well.
Above is a painting by John Singer Sargent in grayscale. By taking the color away from the image, little emotion is felt, it is simply a woman seated at a dinner table. While it's a nice painting, and the composition is strong and the drawing is accurate, we are uncertain what to feel about this woman, or what she is feeling. But add a cool color scheme and we immediately get a sense of emotion and mood.
With a cool palette, the feeling of calm and quiet is evoked. The woman is sitting comfortable in the atmosphere. Maybe she's just had a wonderful dinner with her husband and dear friends and is relaxing before she gets ready to turn in for the night. Sounds like a nice story for the painting. But, make it a warm color scheme and it is a very different mood.
Now there seems to be a disquiet to the scene; an underlying tension. And we can make up a story behind this feeling, too. (Note: the warm scheme is the one Sargent used.)
Here's an illustration by Saul Tepper called The Make-up Time. I've transformed it into grayscale, cool colors (his palette), and warm colors. You can click on it to see it larger. In the cool colored version, you can sense that the fight is over, and now is the time for the couple to work it out. And you believe they will. However, with the warm colored version, it says anger and passion. The clenched fists of the boy have a very different meaning and you are uncertain just how bad this may turn out. You can see how quickly it goes from "The Make-up Time" to "The Break-up TIme" — a very different feeling by simply changing the overall hue of the piece.
Color evokes mood better than any other tool in our toolbox. And we as artists must make it our duty to understand how to use it so we can better communicate these emotions to others.