Not sure now, again. I went to my LFS and showed this picture to the guy who is very knowledgeable (I trust him) and without hesitation said it's a MALE. He said the dorsal fin is what one should look at. Didn't buy a fish though since their GBRs didn't look so nice.
I tend to think that is a male in your photo. I'm attaching a photo of a pair, male on top, female on bottom cleaning the rock.
Finding a mate after the fact is not always successful, as this fish selects their own mates. The male may not accept any female. I had this occur with the closely-related Bolivian Ram.
Just for interest, am also adding a photo of a pair of wild caught fish. Generations of tank raising this species has lessened the colouration and resistance to disease, partly compensated for (or attempts to) by "German Blue" and similar trends.