So I bought my Betta male veil tail fish from petco about 8 months ago and it used to be dark blue and since about 3 months ago it has been turning light red. He now only has like a half inch of blue around his head. And at the tip of his mouth. Does anyone know why this has happened? He is a happy swimmer and loves to jump around and everything. He eats fine too.
He may have been a young fish when you got him. Bettas usually do have some color changes during youth and adolescence. I've never heard of such a complete color change as this, but if he's swimming and jumping and eating and otherwise seems happy then I wouldn't be worried about it.
One possible factor could be his food. Most betta food includes color enhancers; I know the first flakes I bought only said "enhance color" without getting more specific, but the flakes themselves were red, as was that betta. Later, we got a completely blue betta and managed to find some pellets that specifically mentioned enhancing blue color, so of course we got them. Unfortunately he didn't seem to like them so we had to feed the red ones, and over time his blue color became less vibrant and his face turned a rather unappealing shade of brown.