Achromatic
Without color. Achromatic grays, like black and white, have no hue and no saturation: only value.
Monochromatic Color Scheme
Color scheme limited to one hue, with variations in value and saturation.
Analogous Color Scheme
Color scheme made up of 3-4 hues that lie adjacent to one another on the spectrum / color circle.
Optical Mixing
Occurs when color fragments are fused by the eye to appear as seamless tonal transitions.
Additive System (rgb)
Color observed as projected light. The additive color primaries are red, green, and blue. When combined in equal amounts, the result is pure, white light.
Traditional Subtractive System (ryb)
The traditional subtractive color system is used by traditional pigments and dyes. The traditional subtractive primaries are red, yellow and blue. In theory, when mixed in equal amounts, they create pure black. In reality they gradually progress to darker and darker hues - never quite reaching pure black.
Contrast of Warm Cool (Itten)
Visual effect created when a warm hue, like red or yellow, is paired with a cool hue, like green or blue.