Should print inks be primary colours?

Suppose printers used red, green and blue ink instead. Which
colours would you mix to make yellow? You couldn’t do it.
Mixing red and green light gives yellow because you are
adding together photons of diff erent wavelengths.
But with ink, you start with white ambient
light and refl ect it off the pigment molecules,
which absorb some of the photons. So you are
subtracting wavelengths, rather than adding
them. The printer ink colours of cyan,
magenta and yellow are used because they
each absorb one of the primary colours – yellow
ink absorbs blue light, and refl ects red and green,
for example