Here's an excerpt of a page I've written on Rams that should help you out.
Generally, both genders of Rams I've had, display almost irridescent colors of red, blue (especially if you view then from a 45% angle), green, black, tourquoise, yellow, and orange. There is some 'controversy' as to whether German Rams are sexually dimorphic. Aquarists who have kept many varieties will be more apt to say that they are becoming less and less dimorphic. In any case, there are some main differences between the two genders.
Male
The male will have long black colored 'spikes' extending vertically out from the tip of the dorsal closest to the head.
The dorsal is most often pointed at the tip facing the caudal fin.
The male is larger; the pelvic fins are larger.
Female
The female will have a pinkish colored pelvic region.
The dorsal is rounded at the end.
There are definitely exceptions to this rule but in general it is the most accurate. Since Rams are becoming increasingly more diverse in coloration and size, some aquarists hold opposing views. Ie. there are Blue Ram females with longer dorsal rays (like the Bolivian Ram), similar to many males. As far as I know, Rams most closely connected to the wild form, often show blue spangles/dots on the black spots on each side of the middle of the body. If they contain blue spangles/dots, it most likely signifies a female, however, I have had males with blue spangles on the black spots on both sides of the fish as well (european morphs).
http://hjem.get2net.dk/Best_of_the_Web/blue rams.html
