There are a few types of "flashing" fish. Flashing tilefish and flashing chromis.
The chromis, Chromis flavicauda looks identical to a yellowtail damsels. It's an endemic to Brazil, and is a very deepwater fish. Unfortunately no links (all would be to competitors), search the scientific name and you'll see it.
The flashing tilefish -- Hoplolatilus chlupatyi is somewhat more common, though a really sensitive fish, that's pretty tough to keep.