I have always really loved Rogue in red when she does street clothes, so I'd be up for a change. I like the Lukas Werneck design in both his original green and this crimson version. Or, since they can dredge up old costumes, a rework of the X-Treme costume could be interesting. And I have a strange fondness for the Shi'ar mining costume, even if Rogue doesn't strike me as a "pink" kind of gal.
I agree the green gals need some visual dissemination though. Jean could easily move into one of her non-green costume choices, but Polaris is generally just in all green. I actually love Rogue's 90's get up when the yellow is toned down to a softer light butter (not bright dandelion) and the green is very emerald dark. But a huge no thanks on that orange poncho. Woof.
And I actually prefer Gambit in all black. He's a thief! Even if he won't be in X-Men (which I'm still pitifully hoping for at this point). So no worries about a clash then either.