Gently melt 50g (1¾ oz) cocoa butter in a bain-marie and mix in 5g (1 tsp) powdered colour for chocolate work. Heat to 45°C (113°F), then leave to cool to 32°C (90°F).
Lightly stick a sheet of acetate to a plastic tray with a little oil to stop it slipping and rub over with cotton wool to remove any bubbles. Use a clean, dry sponge or a fine-haired paintbrush to cover the acetate in the coloured cocoa butter. (1) Use straight, fluid motions all in the same direction to create the desired effect. (2)
If you wish the colour to be darker, let the first layer set and go over it again until you have the depth of colour you want. To enhance further you can brush a very thin layer of a different coloured luster dust on top.
Follow the instructions below for spreading the chocolate.