He is beautiful. Why is he yawning? Are you keeping him up? I use to work with little kids at a school and I took one of my bettas to school and had it in the class room one little girl called him Rainbow Boy and he looked a lot like yours....good find!
After my first betta dying on me after only a few short days, i decided to try again.
Hang on dont give up just yet
Water temp?
Ammonia?
Nitrite?
Nitrate?
Also PH?
how big is his tank, whats in his tank?
Also what else is in the tank fish wise?