Yes, the variety known as Yellow Riesentraube came from seeds from one fruit on a plant of all red ones. A somatic mutation, not a seed DNA mutation, and it was stable.
So why not let that one Blush fruit ripen up a bit, save the seeds and replant to see if it is a somatic mutation or an environmental effect.
I've been lucky to see several somatic mutations but they all involved just one branch of a plant that had either entirely different fruit shapes from the original, or colors different from the original.
And I'm sure some of you here have grown Casino Chips, a cherry, that was a one branch somatic mutation from the parent called Casino. Color still red but then cherry in shape and Casino itself was much larger, I think a large plum but I'm not taking the time to go fetch a picture.
Carolyn