Can't specifically help with the fish you're looking for, though with Jack Dempsey generally you'll see more "body plating" on males with the irredesence and females will have it more on the face, some people call it a "blue beard". Obviously you can have feminine males and masculin females, but I find it to be pretty accurate.
On a side note, there's already a sticky I believe. Duanes made it, visual guide to sexing new world cichlids I think...
Yeah female JD'S will have blue gill plating, and males will have colored spotting all down the body. Plus they will get larger.