The colour plaster for the drywall walls in this house combines white clay, finely chopped straw, and earth pigments to form a thick mixture that is applied with a metal trowel.

After the owners chose their colours, the plaster contractor mixes test batches of plaster and lets them dry on a scrap piece of drywall. Then the amounts of certain pigments are adjusted to achieve the desired colour. Different types of clay can also be used to affect the final colour.