i just had to jump in, iv been breeding for a while and my friends who got me into the hobby have been into fish since VERY early 80s........
in my experience iv had a few pieces with white eyes and red eyes that were "infertile" and i took them let them mature and most of them were fertile with a rate of like 3 out of 5 spawns being fertilized.
red eyes are the quick way to try and guess.......much like the dot on the dorsal fin makes people think its a female....only to be a male.