You will need three white or see-through plates. Stick (or just place) to the bottom of the plate, a piece of paper or fabric of a certain colour – yellow, blue, red. Then, using coloured paper or cardboard, cut out circles or other shapes using the same three colours. The task is to sort all of the colours into their respective plates.
When the child has mastered basic colours, include secondary ones: orange, green or purple, and then the rest.
If you already have different coloured plates, use them.