I’m wondering if this is normal looking.Rabbit is a 6 month old Continental Giant and his whites appear to be well white,no redness.His third eyelid does appear to be dark in color and a little red.
The third eyelid can seem more prominent when a rabbit is stressed, but should return to normal when the rabbit calms down. There are also some medical conditions that can cause a protruding third eyelid, like heart problems and thymoma.
It also seems to be more visible in larger breed rabbits. It might have to do with some of them being predisposed to heart issues. Your rabbits third eyelid doesn't look like it's protruding much, but if it's persistently like this and you think your rabbit could have a possible heart condition,, I would urge having your rabbit checked by your knowledgeable rabbit vet.