It's a gray fiberglass insulated aquaculture tank. I did have the overhead light on while netting them.

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=359690&page=14

Originally Posted By: Jim Wetzel
The yellow of females blanches as season progresses unless on diet loaded with carotenoids.


Originally Posted By: Jim Wetzel
When we breed sunfish such as RES indoors, the feed is often supplemented with paprika. Purpose is to increase coloration of eggs. Clear-ish eggs do not appear to hatch as well. The females store the carotenoids as pigment in the skin. The pigment is mobilized each time the female matures a batch of eggs. Females pushed hard to produce multiple clutches in rapid succession get a silvery look.

Snails and the like may not be good sources of carotenoids. Crustaceans like in the plankton, which BG more inclined to eat, are better.