This document discusses color theory and color schemes. It begins by explaining how color receptors in the eye perceive different colors and how colors can be mapped to a color wheel. It then defines terms like hue, saturation, brightness, tint, shade, and tone used to describe colors. Finally, it outlines several common color schemes - monochromatic, analogous, complementary, triadic, square-tetradic, accented, warm, and cold - and provides an example of a double-complementary palette used on a website.