RGB
refers to the primary colors of light, which are Red, Green, and Blue.
RGB mode is used for images viewed on monitors, televisions,
and computer screens.
CMYK refers to the primary colors of ink pigment, which are Cyan,
Magenta, Yellow, and Black. CMYK mode is what we use to print on our
presses.
Please convert all RGB color images to CMYK to avoid
surprises, as there are few colors which look different in the CMYK
color space. For instance, blue looks much richer in RGB color space compared
to printed product in CMYK. By default all pictures taken by digital cameras are in
RGB workspace, and must be converted to CMYK.