Go to the part in the Disney movie where the fairy godmother gives her the dress. After that part, keep watching. Notice how her dress changes from white to blue frequently? I think this is a slip-up, but you let me know what you think.
Finally someone who agrees with me. I know for a fact that the dress goes from WHITE!!!!! to blue, but dosent evryone at the dance? Then when they are outside they are normal colors again because the lights arent dimmed.