When you upload an image file, the simulation divides the image into three primary colors (Cyan, Magenta, Yellow) of the pigment.
You can see the original colors by printing on transparent transparencies and then overlaying them.
three primary colors of pigment
An object has a specific color because the pigment in the thing reflects particular light and absorbs the rest.
When two or more pigments are mixed, they get darker because most absorbable light is absorbed.
Therefore, the three primary colors of the pigment are not ‘red-yellow-blue’ but ‘cyan-magenta-yellow’ which is the secondary color of the three primary colors of light.
In theory, mixing all ‘three primary colors of pigment’ should be black, but it is not entirely darkened by some reflected light.
Color printers use a four-color system of CMYK (cyan-magenta-yellow-black) by adding black to the three primary colors of pigments. This is because black is used a lot in letters, and it is to get rich black in shadows.