It was interesting discussion if it is ok to calculate the ease of getting red using percent of reds. But even it is not ok I was determinated to know what part every color takes if we exclude users who took part in few contest. About an half of users leaves CF before their 5th contest. I have not any stats about robots though)
So for human stats looks so:

If minimal number of contests is 5:

You can try other parameters on interactive dashboard. Hover the mouse over color areas to see more details.
Script code is here.