Simultaneous Color Contrast
Color vision operates like any of the other visual channels in that colors appearance is relative. When we look at a color, our brain detects not so much the color itself, but the contrast between the color and the colors surrounding it. This phenomenon is called simultaneous color contrast. (For more information see simultaneous contrast.)
The color channels also follow the principles of adaptation. When the eye is exposed to a very intense signal of a certain color, it desensitizes to that color.
Spatial Assimilation is nearly the opposite of simultaneous color contrast. When two colors are placed extremely close to each other, the eye loses the ability to distinguish between them. When this happens, the colors begin to follow the properties of color addition and meld into a third color.
Spatial Assimilation is especially important in the modern world because it is the concept behind color TVs and computer monitors. Inside this monitor there are only three colors of lights: red, blue, and green. These lights are so small that it is impossible to see each color by itself. The red, green, and blue lights can appear to be millions of colors because they are so close to each other. For proof, look at a monitor or television (larger and/or lower quality work better) closely or through a magnifying glass and observe the individual tiny lights.