In Collecting Antique Marbles, Paul Baumann gives tables of "relative rarity" with percentages for various colors and features, based on his observations of the marbles he had at his disposal. He tells the sample sizes he derives his figures from. I just tried to skim to remind myself of where the samples came from -- whether they were all his or were ones he had access to in other collections -- but I couldn't find that little bit of info.
If you don't have this book in your collection, I recommend it.