Once you have a palette, this is how you distribute it. Originally from interior design, now the foundation of UI color balance. Prevents palettes from feeling chaotic.
60% Dominant
Background and large surfaces. Usually the lightest or most neutral color. Sets the mood and lets everything else breathe.
30% Secondary
Cards, sections, borders, body text. Supports the dominant without competing for attention.
10% Accent
Buttons, links, highlights, key words. The "wow" color. Used sparingly so it stays loud.