Light grey for groomsmen and darker grey for groom! I love the idea of the groomsmen in a different color suit than the groom! Only the groomsmen would have the dark gray ties and the groom the lighter.
The groom looks distinct from his groomsmen. Here, the groom wears a suit jacket and traditional tie, while the guys don vests and bowties. I also like the idea of the grooms outfit being lighter or darker than his buddies