It's not assumption, it's fact. After creating SVG image i use function getOriginalColors for retrieving all colors used in SVG image. And I see that when I send maxColors = 10, it is possible to get 16. So, based on sharp docs, parameter colours set number of palette entries (in my mind it means number of colors). I checked visually image after sharp convertation and it looks cool. Vectorization also looks nice visually but in result I counted colors used for SVG and it is bigger than my value (10). Mostly, for max = 10 it gives me 16 colors