1.0 link Rainbow Dash Network http://rainbowdash.net/ Narwhal (narwhal) http://rainbowdash.net/narwhal http://rainbowdash.net/notice/3863576 @<span class="vcard"><a href="http://rainbowdash.net/user/32751" class="url" title="MetalTao"><span class="fn nickname mention">metaltao</span></a></span> It's a principle known as colour constantcy. Essentially, because of the lighting in the photo our brain makes assumptions about the colour of the dress that cause our perception of the colour to differ.