No EE is "pure."
There are indeed ways of sexing them though. One is the common way of looking at the comb. The other is by looking at the plumage after it grows in enough. Males and Females have certain patterns they each follow with set rules. It is a part of the fact that most EE's are duckwing based.
White EE's you cannot sex in this manner, but a general rule is that if the chick is turning out mostly brown and black - Females will have a normal brown colored head and chest, black barred or penciled appearance from the shoulders on back to the tail. Males will be a darker, rich red with less of the barred/penciled appearance, and more of a scattered black here and there. The shoulders will eventually grow in a rich, almost shiny red color and the tail will get quite green.
If the chick is growing up to be mostly white and black, a female will again have a mostly white head with an appearance of black penciling or barring on the back half of the body. It may have some salmony orange or red coloration show up on the chest, but that's usually about it. Males will be, again, less of a barred/penciled appearance and more of just simply a splattered or smudged scattering of black through their body. They will also start to grow red and gold coloration on their shoulders and/or neck and back. Their tails will be solid black and have a green sheen.
If the chick feathers out an odd multicolor, but is getting any gold or bright red in the mix, it is a male. If it is simply beginning to look like a wild Quail, it is a female.
Tell me if that was too hard to understand.