First of all I must state that this is official Mass Effect concept art and that I take no credit for it. This is copyrighted material. All I've really done is photoshop the male krogan to what I believe a female krogan would look like.
Now that that's out of the way, I'll explain my thought process. I started by trying to remove all traits that would be distinctively male, meaning all traits that males would use to impress females, such as the larger hump, larger jaw and the spikier bits in their plate armor. After that I decided to widen the hips a bit, a distinctive female trait due to child birth. I even slightly slimmed down the waist.
What I imagined of Krogan childbirth is that they wouldn't lay eggs, instead they would give birth like mammals, only without going through the stage of breast feeding, meaning no breasts. I imagine Krogan children would be eating solids practically from birth and already be quite self reliant, something like an 8 year old human child. This would make sense with the "rapid expansion" idea of the Krogans from before the Genophage. I dont think the children (or runts) would even be entirely raised by females, rather, they'd be raised by their clan. Being trained for battle from birth.
Given all this, I think the female krogan would look as such, not very different from males, but different enough to serve practical uses. The mention of a female warlord in the game was already enough of a giveaway to make me think females are just as capable at fighting as males.
Oh, and the female with make-up pic was partially just for fun, but I do think the violet eye shadow makes it look better and more female, the lipstick was just for kicks