A new analytical method represents the surface of a color gamut for a reproduction process based on three or four primary colors by a single, closed expression directly in CIELAB. The method is based on the similarity of a color gamut to a cube (the CMY cube), and this similarity is represented by a kernel gamut. The kernel gamut is distorted by distortion and scaling functions in order to match the color gamut. The color gamut is fully represented by the distortion and scaling functions. The total number of their coefficients is below 150 at mean visual errors of below 2.15 ΔE_ab units.