Yeah, that's a pale blue, but I find it hard to alieve (and, had I not read Generalizing From One Example, I'd also find it hard to believe) that a sizeable fraction of the population find it pale enough to call it "white" non-trollingly. This also applies if I look at it on a dark background such as the left panel of XKCD with my screen's luminosity set to the maximum. (The only condition in which I would call such a thing “white” is if I thought it only looked like that because of the ambient light, but under so blue a light the dark parts of the dress would look quite black with hardly any trace of yellow whatsoever.)