dont have to be red, bettas are one of the only fish that have differant color eyes within the species so it could very have red eyes and not be blind. from what i hear bettas are very good at adapting to being blind so you might even have a hard time determineing wether teh fish is accually blind. because they dont have ears per say, they sense vibration very well and know when there is food around throgh and can tell when u are near, i dont see how it would be any differant than haveing a normal fish. your fish may just be becomeing blind in which case it wuld have some trouble getting around as its used to being able to see things. you can ask wuv about the one she had, im sure she would know how to tell how a blind betta behaves
or ask me or bettamomma .my blind guy is for sure blind he doesnt repond to anything except noises ,mine also likes to eat he eats alot (hes big now ,i was right when i said anything in our house for a week gets fat).
They can actually scent food out. They do have nostrils, and they can smell. Also, they can feel the slight disturbances food makes in the water, when it's falling, or moving, or when it's just been dropped in.
The only reason im thinking that he could be going blind is because of when i feed him. He wont take the pellets unless its right in front of his face. My other bettas will get it. It will take some of them a while if it goes behind them but Twist dosent. I will post a pic and you guys can be the judge