I don't think anyone really knows what's going on with his eyes, kind of like Jason's hair haha. The movie version (the animated one that DC produced) has him drawn with green eyes, but I've seen him with dark ones and blue ones. The comics tend to stick to the dark brown/black, but that may or may not be due to the coloring style of the comics that I've seen him in. It's a lot of rich, saturated colors and blacks. Fan art likes to have him with blue eyes, maybe since all of the other Robins did? Who knows.
But uh, yeah, anyway...good observation lol. Sorry for my rant-out-of-left-field.
Yeah, it seems it was the style of the artist, I checked it again, and everybody had huge black eyes o-õ I think it is so awkward when every Robin has blue eyes, Bruce Wayne sounds a bit creepy when I think about it.
That's one of the things with comics; artists can take liberties and then it confuses people haha. If I remember correctly, waaaaay back in the beginning Jason had red hair and then dyed it to look more like Dick. I suppose it's meant to be clever, like a physical manifestation of the similarities that Bruce sees between himself and all of the kids that have been Robin. There was some fan theory floating around that said they were all 4 different parts of Bruce's personality? I doubt THAT was intentional, but it fits well with the creepy we-all-look-just-like-Bruce thing. Oddly enough, the ladies that have been Robin didn't look like him at all lol.