It appears to me as blue and black. Definitively. First viewed as a whole image, full screen on a tall portrait IPS and then checked on a second landscape IPS (these two screens long ago adjusted to show matched colours).
Both the black and blue appear to me somewhat blown out. Actually, the mottled black almost appears as a mutant non-colour unlike anything one sees in real life (the colour balance algorithm of a digital camera subtracting blue from the black is a perfect explanation for this).
If I scroll so that I can only see the top of the dress (down to just past the horizontal black band across her upper back) I can almost conceive of how some people see this dress as white and gold. What I actually perceive is an ambiguous image under false, untrustworthy light.
In my bedroom I have several unusual light sources which I regularly use. In addition to an incandescent lamp, there an extremely yellow bug lamp and a bright and narrow-spectrum blue LED light intended to shift circadian rhythm.
I love the yellow bug lamp because it's initially so dim I can turn it on briefly while my wife sleeps to find my socks, plus I often use it for reading late in my day so as not to expose myself to blue light. I also had red and green light sources for a while, before I discovered yellow bug-light perfection (the red and green bulbs were 40 W coloured-glass bulbs that constantly smelled bad because they instantly baked any stray dust—a failed experiment).
I have pretty good sense in my bedroom of which colours are more or less trustworthy under vastly different lighting conditions. Even under my narrow-spectrum blue light (in an otherwise dark bedroom) I can't make anything white look like this photograph. In my bedroom under a pure blue illumination (75% between 450 and 480 nm, centered at 464 nm; with 490 nm attenuated by 10 dB compared to the spectral peak) the highlights on my white sheets where the light is strongest are more saturated, and the dimmer regions are less saturated, opposite my impression of this photograph.
Perhaps people who spend a lot of time watching TV in dark rooms where people are wearing white clothing are conditioned differently.