CMYK (cyan/magenta/yellow/key black – 4 col process)
This is used in the most common printed process called litho or offset litho
RGB (red/green/blue – screen based)
Greyscale (Black and white continuous tone, any shade of grey such as a black and white photograph)
Duotone (when a continuous tone image is printed in 2 or more spot colours – this term is also generally used when describing tri and quadtones.
Spot colour (one or more specially mixed colours as opposed as a result of a CMYK or RGB mix)
Mono (like greyscale but with a coloured ink, ie:one colour only plus the colour of the material it’s printed on)