From the article I linked earlier:
 

What I wonder is that there is clearly black and white cloth visible in the leftmost side of the picture. There is a reference, same lighting, exactly same time. 
Anyway, the dress manufacturer has confirmed it's black/blue.

I understand people thinking the dress is in shadow, but that still doesn't explain why they're not seeing the blue/purple. After all if the dress was white, it would be a grey color in shadow, not periwinkle. Again, it's not a biggie in the grand scheme of things, but it has made me realize how many people apparently don't perceive colors properly.

I think for the record I have pretty good color perception, I was a master at the phone game Blendoku which has you arranging differently colored chips on a board so that they all blend into each other from all directions. There were levels of that game which had colors which were so dark they were almost black, and my girlfriend couldn't even see them because they were too similar to the black background. Whereas I was picking out minute differences in their shades and arranging them into rainbows. I sure as hell don't have 20/20 vision but I think I have pretty sharp color!

sharke
After all if the dress was white, it would be a grey color in shadow, not periwinkle. Again, it's not a biggie in the grand scheme of things, but it has made me realize how many people apparently don't perceive colors properly.

Not necessarily. There are a thousand shades of white. Ever notice how shadows on snow look blue?

When I saw it on TV I was convinced that the dress was white and gold.

The dress in the opening post appears blue vs white and blackish vs gold.

Weird hey.

In sharke's sampling the top rectangle appears a brownish sort of colour while the bottom is blue.

It's a lovely shade of black, isn't it?
Can we all agree it's rather an ugly dress?

Color is a conceit created by the mind... well that's my take on it anyway.  Otherwise it can't really even be proven to exist. Funny thing color is.

I don't care what color a dress is as long as it comes off.

I can see both a blue/black dress and a gold/white dress.

Look at the panel at the top of the dress, this is either black with a lighter highlight or it is gold with a darker shadow.

If you let your mind flit between these two notions then the dress colour changes from blue to white relatively.

jbow

craigb

That reminds me of the above and below images.  The color of the middle cubes on all sides above is the same (provable by pulling the image into a photo imaging program and sampling).
 
Sure looks like brown on top and orange on the main face towards you, doesn't it?
 

The top and the bottom are actually the same
color.
 

 
One last one.  Squares "A" and "B" above are actually the same color.
 
Conclusion?  Our brains are messed up! 

One last one... no they're not, at least not on my screen. I never claimed to have a brain, I have never seen my brain so I'm not sure if I have one or not but if I do... well, it has been disassembled and reassembled. There may have been some parts left over, or maybe that was earwax. How can those squares be the same color? Did you get this off Facebook, that would explain it! LOL.

Get a piece of paper and cut two holes in it that line up with the lettered squares, you can then see they are the same colour rather than allowing your brain to make things up. :)