Last year I saw Kumato tomatoes sold at the supermarket, they are purple-orange sometimes with green patches and are rather sweet tasting. It said the company who produced these dont sell seeds and only special people get the priveledge of growing them.
I took some seeds from the fresh tomatoes, and grew plants from them this year.
This is what the "parent" tomatoes looked like.

I grew mine, and noticed they are smaller, and vary in color from pure purple, to half red/purple, to fully red! Nowhere in the companies description do they say they are supposed to be red! So in fact they vary in color, and each color has it's own taste. Red are most tart, purple are most sweet. I found this interesting.