it's blue and gold if you open the image up in paint.net and zoom in you can tell my each pixel that they're just variations of baby blue and a dark gold
It's blue and black, regardless of colorpicking. The girl was interviewed, saw it in real life as blue and black. You can find the dress on Amazon, clearly blue and black.
Supposedly it depends on your mood and overall eye sight, depending on those things your rods and cones in your eyes differ from the rest, giving the dress a different visual perception per individual.