There was a thread on askscience yesterday about it that you might find interesting:
http://www.reddit.com/r/askscience/comments/2xbfxp/what_color_is_the_dress_why_do_some_people_see/@TalkingFan:
While there is sometimes a slight difference in the shading of images depending on whether they use CMYK or RGB, the point here is that different people see the
same image as different colours. This is because some people interpret there to be a slightly blue coloured light on the dress and others see a slightly yellow coloured light on the dress. This is well demonstrated in this XKCD comic:
http://xkcd.com/1492/