Junior Bridesmaid Dress

So I'm leaving in 15 minutes to go look at junior bridesmaid dresses but I have a concern. So the bridesmaids are wearing a dress that's pretty expensive ($200) My junior bridesmaids are twins so I don't want the parents to have to pay for it (and FH and I didn't budget it) so we're heading to Davids Bridal to look at dresses. I know that they don't carry the fabric or color that the bridesmaids will be wearing. I was wondering if you think it would be weird if I put them in a darker green dress with a different fabric. I honestly don't mind the color difference, but I think the fabric may be strange. I tried to look for pictures of the Jr. in a different color dress but I can't seem to find any.

Any thoughts on this?