It's the way pigments reflect the newly formed colors when mixed. Pigment paints are usually made from finely crushed particles, or powder combined with a clear binder such as oil or acrylic. Colors mixed from pigments usually contain mixtures of colored particles too small to see. For the most part, this is not the case with clear colored inks and dyes. Transparent inks and dyes are usually dissolved solutions.
Colors combined as solutions usually mix to become a single solution of the new color.
The pigment paint colors do not physically combine in the same way transparent inks and dyes do . So it seems that identical shades of inks and paints do not always produced the same results. Even though transparent magenta and yellow may mix to produce a brilliant saturated red , these same two colors mixed as pigments appear to produce reds that lack the same vitality. The red, yellow, and blue trio is still used by many schools to introduce children to color, or to the wonders of color mixing. The familiar starting hues of bright yellow, saturated red, and intense dark blue are most likely to hold their attention.