For those unwilling to grow GMO stuff: Jim Meyers at Oregon State used conventional breeding to produce a purple tomato and released 'Indigo Rose' in 2012; since then many better high-anthocyanin types have been bred from that starting variety.
These are not solidly purple throughout the fruit, and the flavor in most is inferior. Breeders continue to improve these lines and maybe someday they'll be a great one.
Incidentally, the "black" tomatoes (like 'Black Krim') are unrelated to the above, and don't have very high levels of the healthful anthocyanins.
