E/_ means the horse is black. If his mother was red he is E/e (surprised it doesn't say that). The red gene is recessive so he is black. The red is almost as if it does not exists, it just means if he had offspring they would have a 50% chance of getting e instead of E, it doesn't mean anything to your horse.
No agouti means he is black. So he is obviously a fading black. Nothing else he can be genetically.
There is a theory that E/e blacks are more likely to fade than E/E blacks, but regardless- both are black, some fade, some don't.
Well he won't be any darker at night then he is during the day
. Sun bleaching bleaches out the color of his hair, it won't come back. So if he looks darker its just because it's the lighting not him.
Make sure diet is good and sweat is gotten rid of, even then he probably will still bleach. Who knows what his owner did differently. You can try paprika, I've heard lots of good things, but short of keeping him in from the sun or constantly blanketed there isn't anything that will work 100%. He is what he is, and I think he's lovely :)