Tradition is for the MOB to be either a shade lighter/darker than the bm's. But then not everyone follows this tradition!
my bm are in aqua, my mum is in aqua and my mil is in gold.
my mum actually picked her outfit before i picked my bm colour because i couldn't decide what i wanted so i had 2 swatches and waned my mum to pick closest too and that would be the colour! then day after i ordered my bm dresses!
both my mum and mil are going to be in similar styles too!!
i would only be peeved if my mil had picked aqua!! since my mum's in it or if she wore white/ivory to out do me!
apart from that we're playing happy families :)
x