Sketch in full colour. 4 colour ball point pen Includes the colours Cyan, Magenta, Yellow and Black Can be used to create every colour by combining the 4 Includes a mixing guide on packet Every colour can be created by combining the 4 colours; Cyan, Magenta, Yellow & Black. The CMYK process is used in printing to build up full colour images, and now you can use that same process to create full colour art with this ballpoint pen. Change inks with the sliding selectors, coloured ink tubes in the clear nib provide visual confirmation. Experiment, doodle, sketch, get cross-hatching and get creative, but most importantly, never leave home without it.