Based on the photographs of screens that I have seen, this seems to be true image persistence, meaning that e.g. a blue subpixel being left on for a long time w

Based on the photographs of screens that I have seen, this seems to be true image persistence, meaning that e.g. a blue subpixel being left on for a long time will not immediately turn completely off when instructed to. That’s the only explanation I can think of for photographs I’ve seen of color images remaining (with the same colors, just fainter) after the screen was instructed to switch to solid grey or black. If my impression is correct, it must be a different phenomenon than the one you’re describing (which I’ve also always heard stttributed to OLEDs), where subpixels will output less light over their lifetimes (and perhaps the dimming-over-time curve is different for different colors).