There are two types of primary colors - additive and subtractive. Additive primary colors are red, green, and blue light, which when combined produce white light. Subtractive primary colors are cyan, magenta, and yellow pigments, which when combined produce black. The color we see is determined by which wavelengths of light are reflected off an object's surface, while the rest are absorbed. Computer screens use red, green, and blue light to display colors by adjusting the intensity of each color.