Four-colour process

The four-colour process is the standard method for colour printing. It involves layering the transparent inks cyan (C), magenta (M), yellow (Y) and black (K for key plate) in tiny dots to create the full spectrum of colour. The addition of a standardised colour bar to the printed sheets using the three primary colours and black. It enables the printer to assess the performance of the press by comparing the colour on the bar to that of the approved colour proof.