On my first trip to the V&A, I noticed this symbol on a few boards at the V&A but could not figure out what it meant on my own despite examining the room and all the information boards nearby. To me, the symbol itself looked like a "seeing and unseeing" sign. But seeing and not-seeing what? Colour? Light? Everything? Not seeing anything at all? A hidden thing to be seen inside the picture? It was a mystery. At first I thought it might be a warning that if one was colour-blind then the picture would not appear as it appears to people without colour-blindness. But then looking around at the few works that had the symbol, I felt that could not be the case as the works which bore the symbol seemed so varied in colour.
Eventually we asked a gallery manager what it meant. He told us that it meant that for that specific work, the V&A had produced a special information guide of some sorts for the visually impaired. Unfortunately, he could not find the one in the room for us though, he said it might have been damaged or taken away by some other visitors. He also could not recall what it was like, but on further prodding from us, eventually went to speculate that there might be a special "tactile board" with the painting in exaggerated relief - something which could be touched by visually impaired people that would give them a feeling of what this beautiful painting looked like.
I spent the rest of the trip to the V&A looking for this apocryphal seeing-replacement board. Unfortunately I did not find anything that was like that, only large print gallery guides, so I still don't know if there truly exists such a "seeing aid" to help the visually impaired experience the works in the museum!