If you’re painting a light colour over a white wall, you do not need to use a primer. If you’re painting light coloured walls with a dark colour, we recommend using Limewash Undercoat Dark. If you’re painting dark coloured walls with a light colour, we recommend using Limewash Undercoat Light. When painting bare plaster, we recommend priming the wall with the undercoat that matches your chosen paint colour to aid adhesion.