it's a female. my jack dempsey is the same color just the top fin is much more red. i love that little beautiful red line. they look so good on JDs and btw i got richardhmc addicted to JDs lol.
Also, Richardhmc: My female didn't start showing colored spots on her sides til about this size too. She's about 5-6" right now and just starting (look at my 90 gallon pic thread). So... if yours hasn't hit the 5-6" mark I'd be patient. Feed her well and it'll color up.