I have been on the hunt for the right grey bag for some time now specifically because I feel it's a color that will go with everything...I agree that it's a great substitute for black, but I actually like brown and grey together !
Yay for grey..keep your bag!!!
I think it would go well with jewel tones like navy, dark red, emerald, purple, yellow, black, white, and jeans. Basically, anything in my wardrobe!! I would stay away from browns. I think it's a good substitute for a black bag.