If it's too red - then it's probably some form of conjunctivitis and would need antibiotic ointment for the eyes. Is there any discharge? If you look at the inside conjunctiva of your own eye - you'll see that it's sort of this nice pink color - their inside lid should be similar.
If it looks irritated, and there is discharge (esp. if it is greenish) and if there is an odor - you probably want to take him in.
