Whats type of color do you add to make a dull color and what do you add to make a bright color?

Answer 1

A bright color is a pigment in its purest state, although brightness actually describes a color's reflectivity and lighter colors are more reflective. Diluting rather than adding white is probably the best way to achieve brightness. Add a little complementary color to dull, or tone down a hue. Blue-Orange, Yellow-Violet, Red-Green.

Answer 2

Complementary colors, colors opposite on the color wheel, will create a dull color. To make a pure hue look brighter, put it next to a dull color.