Changing Colors?

[KrystaK]

I've only had Casper for a month or so but in that time I've noticed he's changing colors.
I bought him as a white/yellowish VT betta, but now around his head is sort of grayish and some of the scales on his back are starting to turn black - and his tale is going from white and blue to blue and red.
I've read about marble betta's 9I think they're called) on this forum and I was just wondering if they're rare or if my Casper could have had a mummy or daddy that was a marble betta....
(And how fast can this transformation in color take? Or is he like a ragdoll cat, they just always get darker throughout their lives?)
Thanks

 

[LilyRose Tank]

Marbles change constantly throughout their lives. The fish can become unrecogniseable to its owner. They are very pretty. Are you able to post before and after pictures, just to make sure he's a marble and hasn't got a case of fin rot

 

[seizethecupcake]

I'm experiencing the same thing with my white--well, he used to be white--HM. When I bought him in October, he was pure, solid white. Now his anal fin is turning red, and getting darker every day!