Dress #1-White
I have a theory about the costuming for the Evil Queen. In the episode "Fruit of the Poisonous Tree," we see a transition in the Queen's personality. She goes from being più of an innocent person, even a victim, to creating an evil plot. As her personality changes, so does her choices in clothing. She goes from a white dress, to a light blue dress, to a dark blue dress. In the episode "A cuore is a Lonely Hunter," the huntsman asks if she is still is in morning and she replies, "The time of morning is over, I simply find that black suites me." It seems as though she literally "wears her emotions on her sleeves."
Dress #2-Light Blue
Dress #3-Dark Blue
Dress (in a way) #4-Black