Some cockers have droopy eyes in which the inner eyelid shows a little. If this is pigmented than it isn't too obvious, but if it is white, then as Nicola said, when they are tired it tends to become a bit red.
Buddy has one pigmented and one non-pigmented inner eyelid (excuse me, I always forget whether it is 2nd or 3rd so I am being a bit vague here!).
I will try to get a photo showing Buddy's eyes!