CMYK-subtracitve colour model. Uses four colour inks.
Grayscale-composed by shaded/tones of gray,varying from black at the weakest intensity and white at the strongest
Duotone-a halftone reproduction of an image using the superimposition of one contrasting color halftone (traditionally black) over another color halftone.
Spot colour- spot color is any color generated by an ink (pure or mixed) that is printed using a single run.