It is not just the visual in this. We live in a world that when presented with two options and told to choose one, we choose one. It is rare to find an adult who can sit there and say none of the above when there is no check box for none of the above. Add in the visual cue and world war three is in the making.
If this dress is in fact the Roman bodycon dress and not some Forever 21 knockoff (Which I would not rule out as possible), it is available in four colors: White/black, Royal Blue/black, Red/black and Pink/black. That pale perrywinkle blue is not an option. Reverting to photography experience, in order to get Royal blue that pale the dress needs to be overexposed drastically. We all should know from experience photographing something in front of a window like this will result in varied exposure, often to extremes. Look to the right in the overexposed section out the window. See any detail? You do? Oh well ok, since the dress is inside and those details are outside the overexposure is to be expected. However to overexpose the dress in front of the window the entire space of the window would be blown out to nuke levels. My cell phone has a very good sensor for a cell phone, among the best in class (was best in it's class at one point) and it would have that very effect attempting to overexpose this shot. We can see details though, this tells me to ignore the color for the time being. All of a sudden average metering makes perfect sense, meter for this = serious over exposure here, Meter for that = serious under exposure there, Phone says screw it meet in the middle and the idiot behind the phone will be none the wiser (Hell, even my SLRs do this).
Examining the exposure with that in mind it is clear that the dress is a stop or two underexposed while the background is a stop or two over exposed. Ok, so if that is under exposed how can royal blue be that pale? Yeah your guess is as good as mine. Moving on to WB....Phone says my user is on Auto mode....is it florescent or sunny, Can't tell, perhaps it is both.....**** it it's incandescent, idiot behind the phone don't know the difference, that is why they use auto mode, right. (My Sisters Mavica, her other latter sony dP&S as well as her HP dP&S used to do that ****, pissed me off to no end) Anyone who has shot incandescent mode in non incandescent light knows what happens, anyone who doesn't, wip out your phone, set it to incandescent and look at something white, like a piece of paper.
Now you have a white dress that looks blue and not the same blue the dress is actually available in as well as a very confused cell phone pictogetter who was fairly confident she took a picture of a white dress.
Lets just say, for the sake of saying so for further discrediting of overexposure of the blue dress. With phones it takes concerted conscious effort to deliberately overexpose a cell phone shot you have to adjust EV manually, which most people who shoot with a cell don't bother to do for any one of a handful of reasons.
Those analyzing the photo are making one major mistake, I made this same mistake while explaining it on Facebook too. Taking the written word as a matter of fact. White balance is called white balance for a reason as white will show any stray color cast (Most commonly the result of lighting type) present while black will not, this we as photographers all know (or at least should know that). So, if black remains constant, Attempting to white balance with autopilot it at this point is futile as sucking out the blue results in a gold silk with a white sheen. At the same time if you WB it to blue the sheen in the black becomes an unnatural muddy orangyred. You stop and manually white balance it to white with the understanding that the silk and lace are black with a slightly tinted sheen you get an underexposed white dress with black silk with a semi-natural pale amber sheen.