Warm colours are the reds, oranges, corals and golden yellows: sunlight and fire. Cool colours are the teals, blues and blue-violets: shade, water, distance. In a painting, warm colours come forward and cool ones recede, which is why distant hills turn blue and a warm object on a cool ground looks closer than it is.
Temperature is also relative, and this is the part that matters for mixing. Every primary comes in a warm and a cool version. Cadmium Red leans orange; Quinacridone Magenta leans blue. Ultramarine Blue leans violet; Phthalo Blue leans green. Cadmium Yellow leans orange; Lemon Yellow leans green.
The rule: mix towards each other
A mix stays clean when both paints lean towards the colour you want, and goes muddy when one leans away. Every paint that leans away brings a little of the third primary with it, and all three primaries together make brown.
- Clean orange: Cadmium Red (leans orange) with Cadmium Yellow (leans orange).
- Clean green: Phthalo Blue (leans green) with Lemon Yellow (leans green).
- Clean violet: Quinacridone Magenta (leans blue) with Ultramarine Blue (leans red).
White cools colours
Adding white doesn’t only lighten a colour; it pulls it cooler and chalkier. That’s why a red tinted with white turns pink rather than ‘light red’, and why so many pink and peach recipes have a touch of yellow in them: the yellow puts back the warmth the white took out.
Using temperature in a painting
- Put warm colours where the light hits and cool ones in the shadows, even on a single-coloured object.
- Cool background elements slightly to push them back, even if they aren’t blue in real life.
- A mostly cool painting with one warm accent makes that accent glow. An all-warm painting feels airless, so leave a few cool notes.
- Mix shadows with a cool colour or a complement rather than black, so they stay luminous.