This dress is very clearly Royal Blue and Black
I have found the images that were originally posted online and some color corrected versions as well.
Left - Corrected Lighter
Middle - Original
Right - Corrected Darker
When I saw the image on the left I still saw blue and black because I quickly noticed that the image is terribly overexposed. Notice the might reflection all along the right side of the image? You know all those stupid filters on instagram? I would venture to guess that is what has happened here. They used something that overexposed the image and the blue areas appear to be light grey or whitish and the black areas have the gold tone that everyone keeps seeing.
This is an eye perception thing, it is a color theory thing, but what it really is, and get ready for this....... IS A LAZY THING!
People that don't care about color or photography or fashion (as much as I don't care about Nascar) wouldn't really care about the color of the dress. So whatever color they see first right or wrong is what they see. That is totally fine, but if this dress were truly white and gold the level of overexposure in that photo would have made the white color painful to look at. Stare directly at the sun painful.
So I appreciate all of you that see white and gold. You are Anne Hathaway in The Devil Wears Prada pre fashion makeover. Don't worry there is hope for you.
Up next.... Bodycon making a white and gold version of the dress as we speak, little Chinese children are working their fingers to the bone.