Betta changing color?

[Danio8]

I’ve had a betta fish for a bit longer than a year now. He lives in a 5.5 gallon tank which started off with a few Java ferns but I have recently rescaled it to include more plants. The gravel is a mix of white and natural colored and always has been. I feed him omega one betta buffet pellets once a day. He gets 50% water changes every week or every other week depending on how busy I am. He started off as mostly white but drastically changed color a few months back to black and red with blue lines on his fins. I just got back from a 2 week vacation and noticed he’s changing again. I read that some bettas have a marble gene where they change colors, so maybe he has that? I’m attaching pictures below. The one where his head is turning a red color is the most recent color change.

 

[Danio8]

Sorry for the bad quality of the first one, it was a screenshot from a video

 

[Andy Sager]

Bettas changing colors is not abnormal. The scales of a Betta have 3 layers to them so as the scales grow, different colors can get created because different parts of the scales get blended together. Then you have the marble gene to add to that so the final colors are not always present when the fish is young. That's the downside of getting young Bettas that aren't solid colors.
This is one of the Bettas I produced in my breeding program. I thought for sure I'd be able to get that tail trait locked in but in the end, the blue border turned into red like the middle then the whole tail turned into the color of mud. So much for big dreams.