I think it's a trick. I looked at this post earlier today and it was very obviously white and gold. I just came back to this same post to test my theory and it is now obviously blue and black. Same computer. Same lighting in this room. Same post, same website. I think what happens is whenever someone generates an image of this dress, it somehow random generates either the white and gold dress in the photo or the blue and black dress. I'll need to do more testing like refreshing the page at different times, and looking for it on other websites, but I'm still sticking with my theory that this is some huge joke and they're two completely different dresses and photos randomly generated when you load the photo of it.