I grew the OSU blue tomato (Tom's seeds) and I got some plants that were regular color and others were blue because the strain then was not stable. Last fall I grew Indigo Rose (Amberroses'seeds) and all the fruits were purple, when ripe they are red in the bottom, they were prolific and pretty but lack in flavor. When mixed in a salad, sauce or roasted in the oven were okay.

Indigo Rose growing with cherry tomatoes

Silvia

Ahhh so maybe that's why my OSU weren't colored up like they were supposed to be. They did have good flavor though so who knows lol.
I hope the indigo don't taste too terribly bad. I'd better just plant a few plants. Your Indigo tomatoes are beautiful.

Even if you get a stable strain, the blue (anthocyanin) pigment in the fruit only shows up where the fruit is exposed to sunlight. That's why the tops of the fruits tend to be blue. Fruits in the interior of the plant or otherwise shaded will have little or no blue pigment.

So (to an extent) you can increase the blue color by pruning off any branches that shade the fruit. No, I am not trying to restart the endless "should you prune tomatoes or not?" debate - just pointing out the role of sunlight in pigment formation.

YES I have one in the ground. Its flowering and small fruit currently. I'll try to figure out how to post a pic.