Betta changing color? ( Angel update!) help?

UPDATE; angel is doing great , our training is going well so far we’re just taking little steps at a time but he’s doing great so far! when i tap on the glass he comes right up! Not always but he’s getting the hang of it. I also made him a custom feeding ring until I get him one online , when I tap on the glass he comes right up to the ring because that’s where food it! Bettas are smart! this will help him so much since he is half blind.

QUESTION; alrighty so recently I’ve been noticing a little change in angel since I've been taking care of him. I’ve looked back at some pictures and videos as well to make sure I’m not going crazy.. Angel’s tail seems to change color a bit, slightly red? When I first got him he was completely white and now he’s changing a bit,
— is this normal ? I want to make sure that angel is okay , if you guys know please let me know! I’ll show images below of when I first got angel vs now so you guys can take a look at that!

He's so pretty! I wouldn't be too worried, he might just be changing colors - my Betta fish do it, especially when they have been rescued out of a rough situation. Just to be safe though make sure to test the ammonia and nitrite in the water, but if they gills are not turning red I wouldn't be worried about ammonia burns.

The colouration appears to be going through the body as well as the fins so it's most likely natural colouration.

Check the water for ammonia, nitrite, nitrate and pH and if that's ok, then it's just colouration.

Don't bother buying a feeding ring. Use a bit of airline and an airline joiner to make a loop and use an airline suction cup to hold the loop in place.