These palettes come from A Dictionary of Color Combinations by Sanzo Wada — a study of natural colour combinations first published in Japan, based on his original six-volume work Haishoku Soukan. It's one of the earliest systematic explorations of how colours work together.
I wanted to work with a restricted colour set — limited palettes force interesting decisions. I settled on four colours per palette, and these are the four-colour combinations from the book, each one a distinct grouping Wada considered harmonious (or at least interesting).
Contrast is the real problem with some — a bright background paired with a similarly bright foreground is nearly unreadable. Sorting the four colours by luminosity helps assign them sensible roles, but it only goes so far. The real fix is mixing them with a monochrome scale, which is what the ◉ ◐ ○ controls do: full colour, a 50/50 halftone blend, or pure mono. If a palette looks bad, try halftone.
You can select one below.