Keep the palette small

Why this rule exists

A large palette feels generous and behaves like chaos. Every additional color is another decision at every turn, another chance for two nearly-identical hues to appear side by side and read as a mistake, another thread of consistency to maintain across a growing product. A small palette, a couple of brand colors, a functional set for states, and a range of neutrals, is easier to apply consistently, easier to keep accessible, and easier for the user to learn as a language. Restraint in color reads as confidence; a riot of hues reads as indecision. The discipline of a tight palette forces you to earn each color and to lean on the neutrals for most of the work, which is exactly where the calm of good interfaces comes from. You are not deprived by a small palette. You are freed from a hundred small color arguments you would otherwise keep having.