Why do newspapers print a combination of four dots – blue, pink, yellow, black – at the bottom of each page?

The four dots – blue (cyan), pink (magenta), yellow and black are registration marks used during printing to help ensure the print is aligned properly. In offset printing technology, which newspapers use, the inked image is transferred from a plate to a rubber blanket, then to the printing surface. These primary colours go into printing a multi-coloured image and have separate plates. Each plate has its individual mark, like the colour dot.