Ribbon To The Rescue!!!
So your dress has turquois from Da Vinci. But you love the dresses at David’s Bridal. However the turquois at David’s Bridal is off from Da Vinci? No biggie!
Why not have your girls wear headbands or jewelry in the color that matches best to the sash on your wedding dress?
For example, take your swatch to a craft store, find turquois ribbon that is very similar, and wrap & glue onto headbands for your girls to wear along with their black dresses?
Or, take that same ribbon and have them use that as the sash! Still want to bring in more turquoise? Have your girls wear jewelry that matches.
There are several ways to bring in that color, and get it pretty close, without having to purchase it at a bridal store.

Picture found at: BV Weddings.