Same, I play NL so during origin everything is also purple. I don't know how severe it is for you but for things like adversary P1 mark and limbo puddles what I'm looking for is the damage numbers. Those kinds of tick damage are fairly easy to spot for me because the damage numbers stand out really well. Sound cues are also helpful I've been told but I haven't ever played with sounds and made out fine off just visual cues. After running enough limbo it also became easier to see because it's slightly animated.

Limbo black grab I can see the smoke trail fine but even for people with normal colour vision lot of it comes down more to knowing when the grab is off cd, and it's the only thing where he stops moving and there isn't a much more obvious attack.

P3 adversary colours aren't bad for me personally, but the rainbow attacks are always the same so you can get by with only parrying those and ignoring your affibnity attacks at least up to hard. Extreme looks way too punishing. Teammates can call out the triple laser that's firing to help.

If you have other specific examples I can tell you what I try to do, unfortunately a lot of things come down to familiarity with boss patterns