While both colours are still wet, use a criss-cross motion to blend the colours together. You’ll need to work quickly with two brushes, blending upwards and downwards simultaneously for a smooth effect.
Blend upwards with one hand, lightly brushing the bottom colour into the top section. Blend downwards with the other hand, lightly brushing the top colour into the section underneath.
Top tip: It’s a good idea to practice this technique on paper or cardboard before you start painting, so that you can feel confident about blending smoothly before attempting it on the wall.