No manufacturer has been able to make a perfect cyan ink that absorbs all red light. Nor have perfect magentas or yellows been manufactured. Consequently most ink-jet photo printers have a combination of 6 or more inks and mix them to achieve the effect that mixing ‘perfect’ cyan, magenta, yellow and black inks would have. Because they use different (closely guarded) chemical formulations for their inks, different printers use different combinations of ink to produce the same colour.