I always saw it as black and blue, until I was scrolling Reddit (as was the style back then) and saw a thumbnail for a meme that had the image of the dress in it. I didn’t pay attention to the thumbnail before opening it, so I only noticed a vaguely light colored object. But when the image loaded full size, the dress was the distinct black and blue I’d seen before. I backed out and took a second look at the thumbnail, and again it looked white and gold.

Now that I’m thinking about it, it could have been the surrounding colors of the screen that effected how I perceived the dress. After discovering this I recreated the effect by taking a screenshot of the dress while zoomed out really far (to essentially turn it in to a thumbnail on its own), but both that and the Reddit thumbnail had a dark background that may have made the dress seem lighter in comparison.