How to mix grey in oil paint

Grey is the most-mixed colour in representational painting and the one most often mixed badly. Black plus white makes a grey, but a cold, flat one that sits apart from everything around it. The greys that make a painting glow are mixed from complements and tipped warm or cool on purpose.

Three ways to make grey

Black + white. Fast, neutral-to-cool, slightly lifeless. Ivory Black is brownish and Mars Black bluish, so even this “neutral” has a bias. Useful for value studies and underpainting.
Complements + white. Ultramarine Blue + Burnt Sienna is the classic; Ultramarine + Burnt Umber for a cooler, darker range; Alizarin or a quinacridone red + Viridian/Phthalo Green for a more chromatic grey. Lighten with Titanium White. These greys carry a hint of both parents and harmonise with the rest of the palette.
Palette mud. The grey left where several mixes met is often the best neutral on the palette because it already contains every colour in the picture. Keep a pile of it.

The ratios that matter

Complement greys are rarely 1 : 1. Ultramarine Blue is a modest tinter and Burnt Sienna a fairly strong one, so a neutral from that pair sits near 2 parts Ultramarine : 1 part Burnt Sienna, then as much white as the value needs — a mid grey is roughly equal parts of the dark mixture and white; a light grey is 1 : 4 or more. Phthalo Green is five to ten times stronger than most reds: a grey from Phthalo + Alizarin wants a dab of green in a pile of red, not a 1 : 1 mix.

This is exactly where recipes go wrong across brands: a Winton Burnt Sienna and a Gamblin Burnt Sienna do not tint alike. The engine-calculated recipes on this site are per set for that reason:

Warm or cool, decided before you mix

Decide what the grey is next to. A grey beside orange flesh should lean cool (more blue); a grey in a warm shadow should lean red-brown. Mix the neutral first, split the pile, and push one half each way with a dab of the parent colours. Three greys from one pile — warm, neutral, cool — is the fastest way to model a form.

Value first, hue second

Match the value (lightness) with white before you chase the hue. A grey that is the right lightness and slightly the wrong temperature reads correctly from across the room; the reverse does not. Check against the reference in daylight — greys shift more under warm bulbs than any other colour.

Questions

What two colours make grey in oil paint?

Any complementary pair: Ultramarine Blue + Burnt Sienna is the most used, then Alizarin Crimson + Viridian, Cadmium Orange + Cobalt Blue, Yellow Ochre + Dioxazine Purple. Add Titanium White to lighten.

How do you make Payne's grey?

Ultramarine Blue with a little Ivory Black (or Burnt Umber), lightened with white. Tube Payne's Grey is a blue-black; mixing it yourself lets you control how blue it is.

Why does my grey look green or purple?

The complements are out of balance. Too much blue or green parent pushes the grey cool-green; too much red parent pushes it violet. Add a dab of the other parent, not black.

Let the app do the arithmetic

PaintMixLab photographs the colour and writes the recipe in parts for the paint set you own. Free for 3 days on iPhone.