The lighting thing depends on your bettas. I know a lady on another forum who breeds halfmoons VERY successfully (shows and wins with her kids) and some of her breeding pairs prefer the lights off, while others don't seem to care. I would try it both ways and see which your pair prefers.
If your pair prefers lights out, then I would turn them back on once the female is out of the tank and the male is tending the nest. It'll make it easier for you to see when the eggs have hatched and when the fry are finally free-swimming.
As far as the eggs being clear...I believe they are mostly clear, but you can see the little fry eyes in them (similar to oto eggs).