When you buy a pale betta in a cup, there's really no telling how he will look in the end. I got a young male who was cambodian colors in the cup. White body, red edging to his fins. He's now fully and vehemently RED all over. My avatar guy (that's what he looked like at purchase) turned out to be a marble. He's a riot of color now - red, blue, teal, purple! I most recently got a female who pretty much looked like a minnow - grey and stripey - and she's developing wonderful teal and red colors.
Don't be suprised if your fellow responds to his new and healthy environment by becoming a fish of a different color