I said elsewhere that this is a scam for the following reasons.
Her Tumbler account (Swiked) shows the initial photo asking what color is the dress. A day or so later she posts a second picture of someone wearing the blue/black version, stating:
this is the dress as i saw it on the day of the wedding. blue and black. It's just that one photo bUT it's so weird???!??
Here's the thing, she does not say the second photo is the same dress ON THE DAY of the wedding, only that the photo shows what she saw.
What most likely happened was she took the first picture on a different day and because it's white/gold, it took on the cast of the lighting to give a blue hue and her friends had a disagreement over the color which started the whole thing, especially if someone is red/green colorblind.
Second, if you look at the top edge of the dress in the first picture you can clearly see what would be considered "virgin" light, i.e. light which is not reflected but directly falling on to the dress. If the claim is that our eyes are fooling us because of the bright background or because we can't be sure what the lighting situation is, this light should produce a different color under it, just as light shining across a rippled surface can produce different colors.
Except it doesn't. There is no transition from the slice of light to the shaded portion. It's one continuous tone. In fact, as the picture shows, there are multiple shadows of different angles and lighting conditions which should produce different colors, but they don't. For instance, under the cape/shawl toward the upper right, the area under the shadow is darker but not a different color.
Further, if our eyes are being deceived by the bright background, covering up all but a small portion of the dress should reveal the true colors because then there would be nothing to confuse us. Except that doesn't work either, the dress stays as white/gold with a blue hue.
And finally, if you look at the edging in the middle of the picture then down to the lower left corner (our left), you can see shadows under the gold edging. If the dress in the picture was blue/black you would not see such distinct shadows as are shown in the picture.
So, the dress in the original picture IS NOT the same dress she shows a day or so later but is the same style.
One final thought. The opposite of blue on the color wheel is gold and the opposite of black is white. However, if you look at what is blue and black in the "good" picture, they are not the correct parts. The bodice is blue which means in the reversed portion the bodice of the original picture should be gold and the edging should be white. Except that is not what is shown. The bodice is white and the edging is gold.
And for the record, I am not red/green colorblind. I pass all the Ishihara color tests without issue.