Etiquette Snob here… lol
It really is up to you and your vision… and of course what they themselves would like to do.
If it is tuxes, then ALL the men can be in coordinating tuxes. Or the Dads in Suits.
Women (Moms) tend to have a distinct idea of what they want. They can coordinate (I don’t like everyone matchy matchy personally… cause the Moms are the Most Honoured Guests, not part of the Bridal Party)
So in the same colour family looks nice… (or SIDE of the colour wheel)
Bridesmaids are say in Powder & Cornflower Blue… then one Mom could do Navy and another a Deep Purple.
They’ll look great with their Men, the B&G, together for both sides, and also in family shots if you happen to have a Sibling who is a Bridesmaid or Groomsman / Usher
OR they could do something radically different… and just take the “feel” of the look you are looking to convey, not the colour per se
So for example in the above scenario, if you were doing a Gatsby Wedding, they wouldn’t have to just stick with Blue or Purple as their tie-in to the look of the Wedding… they could wear any colour of their choosing… but the sytle of their dresses could speak to the Gatsby theme
PHOTO – Example, MOB Gatsby Style (Rose coloured, but colour goes well with Blue & White)
According to Traditional Etiquette, the Bride & her Mom discuss options, the MOB taking her cue as to what to wear from the Bride’s vision… and perhaps shop for the MOB Dress together. And once that is established the MOB, shares her dress info (or a pic) with the MOG, who takes her cue from the info she now has at hand… Bride’s Vision for the Wedding, and what the MOB has chosen. It is not appropriate for the MOG to try to upstage either of these women. If the MOG feels she needs more info / help, she should consult with the Bride (who has seen the dress that her Mother will be wearing)
So in the above scenario… the MOG could opt also to do a Flapper Style Dress… and in any colour of her choosing. Just as long as her dress isn’t any more ornate say than the one chosen by the MOB (ie fabric, beading, embellishments etc)
Hope this helps,