The picture in your first link shows a white and gold dress. I plopped it in MSPaint and used the dropper tool to get the pixel colors.

From a gold section: Red: 126, Green: 108, Blue: 72

According to this, a color called "Golden Brown" is given by: Red: 153, Green: 101, Blue: 21

Which is pretty close, admittedly the dress color is slightly more blue than this, but I personally don't see much of a blue tint. The Black you are looking for would be all 0's, or close to it, which the sample is nothing like.

From a white section: Red: 162, Green: 176, Blue: 211

Which is not really very white, since perfect white would be all 255's.

But lets assume the picture is taken in dim lighting. The picture itself shows a much brighter background than what we see of the dress, so I think this is a fair assumption. In the top right, we even see that the camera is having trouble with this difference in light levels, and it is getting blurred out completely.

So lets just look at the relative value instead. In your Amazon link, a sample of the blue gives something like: Red: 47, Green: 77, Blue: 151

The blue value is triple that of red, and double that of green. Or, blue is about 100 higher than red, and 75 higher than green.

The "white" sample has blue only slightly higher than either red or green. Clearly, this is not just the same color in a different light (unless we are working with some strangely colored lighting here). All values being relatively equal means it is on the grey scale, and being on the high end means it it towards white.

If you want to insist that your first link is a doctored image, then its really irrelevant what color the dress in that image is. But the dress in that image is definitely not black and blue - it looks white and gold, and color samples confirm it,