The female D. compressiceps do have the red-tipped dorsal fin. Males will get color throughout the entire dorsal.
The anal find shape is a good indicator. I've also found that males will start to get a blue sheen in the face prior to their other color and the females will never have a blue sheen.
Female.
I'm inclined to think the same. Occasionally I've seen males that don't start coloring up until 4"-5".