Friend is Blind in One Eye?

I have a friend who is blind in her right eye. If I took a picture of her, if there is 'red eye', the eye which she is blind in is always a different color. If I showed you a picture you could guess which eye she is blind in because it would be glowing bright yellow rather than red like her other eye and like everyone else's. My question is, what is the physiological reason behind this? I am sorry I do not have more information about what caused the blindness. I think it was a tumor that she was born with behind her eye, and when it was removed it caused blindness.