How to Mix Colours in Watercolour Without Making Mud

One of the most common frustrations beginners bring to my workshops is muddy colour. They mix two beautiful colours together and end up with grey-brown sludge. Here's why that happens and how to avoid it.

Understand warm and cool

Every colour has a temperature bias — a warm or cool leaning. Cadmium yellow is warm (leans orange). Lemon yellow is cool (leans green). Ultramarine blue is warm (leans red). Cerulean is cool (leans green). Alizarin crimson is cool (leans blue). Cadmium red is warm (leans yellow).

When you mix two colours that lean toward each other, the result is bright. When you mix two that lean away, you introduce a third primary and the result dulls. This is where mud comes from.

Mix on the palette, not the paper

Always mix your colours thoroughly in a well before applying them. Partially-mixed colours on the paper can look interesting (sometimes intentionally so), but if you want a clean, consistent hue, do the work in the palette first.

Use clean water and a clean brush

Dirty water makes dirty colours. Change your rinse water regularly — a lot more often than you think you need to. I keep two jars: one for rinsing, one clean. Always mix from the clean jar.

Mix more than you need

Running out of a mixed colour mid-wash is one of the most frustrating things that can happen. Mix a generous puddle before you start. You can always save leftover paint on the palette and reactivate it later.

Limit your palette

The more colours you mix, the higher the chance of introducing a hidden opposite and producing mud. A limited palette of five or six colours, well understood, produces cleaner results than a large set used carelessly.

Test before committing

Always test your mixed colour on a spare piece of paper before applying it to your painting. Colours look different on the palette than they do when diluted on paper, and they dry lighter than they appear when wet. A quick swatch saves a lot of grief.