For what it is worth, another anecdote from a community garden farmer. When I took over my current plot five years ago, I ended up with little yellow tomato volunteers throughout. I also had some red cherry-sized volunteers, with good flavor but a tendency to crack. After some research, I thought the yellows might be sungolds, but I did not save seeds. Every year, they came back and mostly flourished, except for one crazy watery summer two years ago. I have been getting a higher proportion of the reds every year since. I saved seeds this summer, and tested a few in my seed growing set-up, and got an yellow result. Vigorous, viney, sets flowers and fruit prolifically. I have no idea what the originals were, and all of my other tomatoes are red romas or slicers. I will start the seeds this summer and take notes on the volunteer plants as opposed to the saved seed ones. I am curious about what is essentially a happy garden accident.
