There is no different between male or female G.B. herons. Juveniles are more pure gray but adults is much more gray than blue. The breeding plumage can be little blueish but still not as strong blue.
Also the bill is yellow/orange. Juvenil's upper bill is little blackish. On your photo the bill is also blue.
Also if you chek the legs, which should be also blackish or brown, on you picture they are blue.
You said this was taken at a morning when the sun just coming up. This time is called "blue hour" because in this time everything can be turn into blueish on a photographs if the WB is around 5500K But still I find it too much blue.
There is any chance did you shoot this with an Olympus camera?
A frend of mine shoot with Olympus and many of his puctures turn into blue like your photo.
If you don't mind I did tried to align the colors a little, how it should be looks. Of corse I gonna delete it if you want.