I can't understand anyone who can look at the left dress and think that it's a dark picture in the shadows.
All the "explanations" basically say the same thing. Those dress shades appear to be white/gold in the context of a dark or dimly lit room.
Which the photo clearly is not. It's so damn bright the entire background is washed out, and light is even spilling over from the background over the dress.
Price tags. In Euros or rubles. And signs in Polish, Swedish, Russian, etc. On all his furniture and appliances, possibly on each bedroom too