you see that xkcd picture right? Both of the drawn dresses are the same colour, so unless
you see them on both sides as the same, I consider my argument proven.
Regarding the xkcd explanation, while I acknowledge that phenomenon, I believe it may be insufficient in this case. I present two pieces of evidence:
1)
http://i.imgur.com/Ktscov0.pngThat is the image from the OP on the left, next to the image from the OP
color inverted on the right. To those who see the dress on the left as white and gold, do you
also see the color inverted dress as
also white and gold? Does that not seem peculiar?
2) For those who see white and gold, look at the image in the OP. Now either tilt your monitor or stand up and
adjust your angle of view to the screen. As you approach 180 degrees, does the white and gold definitely change appearance to blue and black? Now, perform the same test with the xkcd image. Does this same color-change phenomenon
not occur?
Best explanation I've read is that different people have varying numbers of
photoreceptor cells in their eyes. Regardless of what color the actual dress is or how badly flooded the lighting on the image, the resultant colors seem to happen to be in a range where the variances in number of color receptor cells among people in enough to change our perception of the image. When you tilt your monitor, you're "condensing" the area with a given amount of light into a small area, thereby compacting the same amount of blue light into a smaller area, making it more spatially dense, past the threshold where you tend to interpret it as being blue.
Some portion of people happen to have a few more blue photoreceptor cells so they don't as need quite as much blue light in a given area to interpret it as blue. That wouldn't explain the people who have seen the dress
change colors, but while the xkcd explanation seems insufficient on its own, it is very probably a factor, and the relatively smaller number of people who see it change might simply happen to be near the middle range of receptor cells to where the relative colors involved can shift their perception one way or another.