"And those should be a longer color," Cadance adds, nodding to the bridesmaids' dresses.

The bridesmaids themselves, with their gentle protestations of "I think they're lovely," "Me, too," and "I love them," don't seem to agree with this highly specific and useful advice.

Rarity may not notice the glare Cadance turns on her bridesmaids, but they certainly do. Once she feels that they're sufficiently cowed, she turns back to Rarity and reaffirms, "Make them a different color." Then she turns and leaves the room, with the bridesmaids following a moment later.