The dress is ACTUALLY blue and black, so why do most people see white and gold?
Well the reason is simple. Our brain is good at taking in information and reasoning a bunch of things that aren't there.
Look at this image
The answer is yes!
Actually, B looks different because your mind sees a contrast with squares next to it and a shadow over it. You think it's lighter because your brain knows that if there was no shadow, then the square would be lighter than A. It processed information that wasn't actually there.
That's what happened in the great dress picture. The lighting and background made it look like it was white and gold to some people because their brains were filling in information that wasn't exactly there.
Source: Buzzfeed Article about this dress.