CMYK

monotone.

One colour screen prints by Kate Morross.

Duotone.

Duotone.

Artwork by Rob Ryan.

Spot Colour.

Artwork by Sophie Henson.

Greyscale

Artwork by Sophie Henson.

Duotone

This piece is by Sophie Henson.
I like the use of overlaying the two colours but slightly offsetting them to create some sort of optical illusion.