Okay, I really shouldn't, but I can't quite supress my computer geekery right now, so let's do an RGB analysis of the dress.
Averaging over the mid-shaded patch on the dark field on the top of the dress, I get the RGB values 0x54, 0x45 and 0x2A, which is this colour:
████████
Doing the same over the middle of the shoulder-arm-flap-thingy gives me 0x7D, 0x85 and 0xA0:
████████
So, taken out of context, that's neither black, gold, blue nor white. That's brown and... blueberry milk? No wonder people se different things...