WHAT DOES GIANT KOI FISH MEAN?

I purchased what I assumed was a Koi betta - mainly white with a little bit of pink and black. He has wholly improved colors, and now he is largely blue and black!but now it’s back to pale with a number of specks of black. His entire body scales have also started getting to be pale. Is this all-natural or anything Improper with my tank?For the ta