My daughter is having an informal wedding in a park, colors pistachio green and ivory. I found a sleeveless dress in a close shade of green but not the same as the MOG. Hers is very dark and in a print...mine is toally opposite (full skirt, chiffon type material, below knee length). Should I opt to change to a green that matches hers or does it matter if the greens clash (it's so difficult to find the same shade)!
She was supposed to coordinate with you, not purchase her dress first.
Your dress should blend or contrast with hers and not match either her or the bridesmaids' dresses. If yours clashes, why not try a color that contrasts.