If you have orange males, they may be lighter/paler than the females once they reach a few inches in size. May not be the case for generations a long way from wild, but has held true in some colonies I've seen.
The most reliable way is to vent them. Egg spots seem to correlate to dominance, but my most dominant couple of females have as many or more egg spots than my subdominant male. Behavioral approaches are also unreliable, as my females are much more likely to fight one another than the boys are; the boys have their hierarchy 100% clear and don't mess with it.