These fish certainly are products of their environment. This Golden coloured Barra came from around the darker tannin stained water and its colouring reflects that. The fish with more silver colourations come from the cleaner open water.
Lilypads provide the perfect environment for smaller fish (sometimes bigger fish) and the darker stained water that oocurs around them provides the perfect ambush point for these growing fish. A kind of Barra nursery if you will. They look absolutely amazing too and are a good sign you are in the tropics!