I have gone far too long without posting about how we see color. Color is an important aspect of many forms of art including paintings, sculpture, drawings, and collage. Imagine a painting of a fruit bowl in which the apple is orange, the grapefruit is turquoise, and the orange is burnt sienna. How would you know which piece of fruit was which?
A blob of green paint is not itself green. Sound confusing? We see objects because there is light (from the sun or the moon or from light bulbs) to illuminate them. This is true of color as well. That blob of green paint looks green because it soaks up all the light waves except the ones that ones that are the right length to look green.
Have you ever hung a prism in a window on a sunny day and seen little rainbows bounce on the walls? The prism filters the white light by slowing down the waves and reflecting them in different directions. Some waves are slowed more than others. The slowest (longest) waves look red and the fastest (shortest) waves look violet. That blob of green paint acts kind of like the prism except that instead of releasing all the waves, it absorbs some. The make up of that paint allows it to reflect the green waves and absorb all the others.
Because it is light that allows us to see color, our eyes will blend red with blue if small dots of each color are placed close together. This is the idea that Georges Seurat used when he experimented with pointillism.