Lulu, my black Plakat, looses color when she's stressed. she'll go from rich black, with red on her fins, to an ugly light brown with rich black stress stripes, and the red will turn a dried-blood color.
when Caroline, my cambodian girl, gets stressed, the red on her fins becomes muddy red and see-through.
the most amazing color change, though, is my HMPK dragon girl. for reasons i can't figure out, Chappy went from a beautiful cream-bodied girl with beautiful green-blue scales, to a brown pineapple with metallic blue on her fins. ._____o lost all her shiny scales, except a few on her eye, and is quite plane looking, the generic way for females to be described by non-betta-lovers.