Grey looks like the quiet option on the colour chart. In practice, it's one of the hardest-working colours you can own. Graffiti writers use it for outlines, shadows and 3D blocking. Illustrators use it to build depth without the harshness of pure black. Model makers and customisers use it as a base coat as well as a final colour.

Grey also works with almost everything else in your kit. A mid-grey sits behind bright fills and makes them look stronger. A light grey softens a highlight without washing it out. A charcoal gives you a shadow that looks natural rather than flat. If you only carry a few cans to a session, a couple of greys will cover more jobs than almost any other colour.