What's really fun us when they start breeding/courting/bullying each other, you can see the colors change like an electric light. I remember the first time i saw a turquoise rainbow do it i thought I was hallucinating.
Sorry I caanot see your images on my work PC, but I have Bosemani's and they 'fade' when sleeping or just waking up in the morning. In fact, I think nearly all fish do.
Ironic you posted this, I happened to be checking my tank this morning when the lights came on and I panicked. The rainbows were very similar to yours, almost black in front. Literally after about 3 minutes you could see the color change! Pretty amazing IMO.