A Horse of a Different Color

Perhaps you had the disappointment of having the color on your printed piece look somewhat different then if did on your computer monitor. There is a scientific reason for this - the RGB (red, green and blue) phosphors that create color on the computer monitor are capable of producing more colors than the three process printing inks (cyan, magenta and yellow or CMY). And the process printing inks, when combined cannot always match exactly the single hue of a PMS spot color.

To put it more simply - there is not a perfect overlap in the range of colors that are both visible to the human eye, reproducible with RGB additive color (like on a computer screen), and reproducible with CMYK subtractive color (like a printed newsletter). Whereas the human eye can see billions of color, RGB can reproduce 16 million and CMYK printing 5-6 thousand. So some colors will convert from RGB to CMYK fairly well (because the color is in the CMYK color gamut).

To illustrate, try this exercise. Using PageMaker, Publisher, Quark XPress, InDesign, or PhotoShop, convert RGB blue to CMYK. Watch what happens to the color. Does it turn to purple? Now reduce the percentage of magenta by 50% and watch it turn back to blue. This is a dramatic example of how additive and substractive color spaces are not perfectly overlapped.