You may be surprised to find out that when any photos or pictures are commercially printed they’re printed out of 4 inks. CMYK.
C for Cyan
M for Magenta
Y for Yellow
K for Key or Black
CMYK is the standard print terms for professional print, most of the time it’s referred to just as four colour process. By overlaying each of these colours you can create an extremely wide range of colours.
If you really want to get into the science of it, feel free to click here.