We don't think they are juveniles, just because they have been around here for over a year.

Does the color of the bill have anything to do with what sex they are?

The male will interact with one of the lighter billed swans, but will have nothing to do with the other. The one he won't have anything to do with has a slightly thicker neck (which we read may be indicative of being a male), but their bill color and bump on their bill is nearly identical.