Absolutely brilliant idea! And we know from cave paintings that colours were used. Also (can't remember where I read it, alas) there was an item about some 60,000 year old make up found - in a clam shell and made of hog lard mixed with dyes. One even had ground shell in it - the shiny part - to give glitter make up!
Nothing new in the world - except perhaps, the EATING of grains, rather than using them for personal adornment!