Well executed, I especially like the sound and visual effects when clicking a wrong shape. As others have mentioned, at some point the colours are too hard to distinguish without the need to. If, for example, you allow the red, green and blue components each to be multiples of 64 you'd get 64 different colours, then increase the number of possible shapes to, let's say 8, and you have 512 different combinations in total. Instead of just relying on colours you may add textures (or just use textures for the colourblind), like points, lines, hatching, waves etc.