I like experimenting with lighting. Right now I have two 6700k lights with a yellow tinge on the out sides of my tank with a 10,000k in the middle. Once my 6700ks burn out i plan on picking up some more 10,000k or mybe a 50/50 they will bring out the colors well in your jack dempseys.
Your tank looks very nicely setup btw, ya i agree not breeding dress, they usually get much darker but it looks like there on there way possibley. What size tank is that?