CYMK is an accurate way of representing colour for print format. It works on the basis that inks in the colours Cyan, Magento, Yellow and Black overlap they create a broad spectrum of colours.

In printing presses, rollers of each of these four colours are pressed on top of eachother one after the other at different intensities. These make up the colour document that you eventually see.

The four colours Cyan, Magento, Yellow and Black are also called the 'Process Colours' in printing-jargon.