Plum Semi-Permanent Hair Colours Recommended as part of a balanced collection... giving hair a delicious red-purple look, Plum is a cool and warm colour, with its mix of blues and reds. For the most vivid results, we recommend applying to pre-lightened hair. The colour on the pot is a simulation of the colour on a level 10. Soft, silky hair never goes out of style. That’s why all our colours contain a conditioning formula that nourishes hair from first application.