A male JD will have coloration of blue/gold/green spangles spread relatively evenly across his fins and body, whereas a female will be much less colorful having fewer spangles of color across her body and fins, but will have many more spangles of color around the Gill Plate behind and under the eyes, giving her some what of a beard of color.
The male JD will be slightly larger, whereas the female will look just a little bit more scrunched up, I always thought female JD's looked a little more "stubby" IMO
Lastly, The fins of the male JD flow much longer, and you will see them extend much longer than that of the female, whose dorsal and anal fins look like they end rather abruptly at the caudal fin, not extending to or past like the male.
Once you know the tricks, the JD is one of the easiest cichlids to sex, but even these visual aids can throw you off, the only positive way to tell is through venting = looking at the reproductive "areas" of the fish.
A male will look like o0 under his belly,
While a female will look like 00.