I personally am not color blind but one of my good friends is. He struggled in E6S, E7S (couldn't tell the difference between the portal colors), P3S, and I'm pretty sure he'd have a similar problem as E7S in P4S as there's purple/blue tethers. While I appreciate that so many things are clearly telegraphed, the game also fails at telegraphing other things in an accessible way. Like look at E12S door boss, there's colored tethers going to each portrait but there's also a sound cue for each tether, which was great. But there's no way to tell the difference between the blue and purple tethers in P4S if you have certain forms of color blindness. And even as a person without color blindness, P3S was a nightmare that wasn't helped by me having a professionally color calibrated IPS display so the orange was even more vivid.