The first step to changing someone's mind is acknowledging that you probably won't be able to. The other commenters are right, the red pill is stupid, it's annoying to argue with them, and you'll probably fail the delicate act of ideological conversion. Still want to give it a shot? Great!

Depending on how deep down the rabbit hole they are, the answer is it could either be impossible or it's a long term dedicated effort. First you should learn a bit about cult deprogramming techniques, as while the red pill isn't really a cult it is an echo chamber ie. a mostly comprehensive view of the world that has built in answers that insulate from external dissent. The red pill tends to provide community, some degree of lifestyle improvement, and a feeling of secret insights into society / the world, and it's very rare an individual will give those things up for the sake of something as abstract as logical consistency.

You need to slowly provide alternatives to whatever positives the red pill provides, which while annoying is possible because the red pill sucks. The online sense of community is tenuous at best, so be their friend and connect them to other friends that'll entirely replace that aspect. Additionally, the lifestyle improvement aspect is rather generic and can come from anywhere. Ask them what specific red pill people they follow and provide a gym / motivation YouTuber that better provides whatever motivation the red pill gives.

The final element is the feeling of insight into the world that the red pill gives. This one is ironically the least important to changing someone's mind and the most difficult, as in order to successfully provide alternatives you likely need to understand the red pill ideology better than they do. Nothing a red pill person says should stump you, you should have heard it beforehand and researched it and thought of better counter arguments. If they mention hypergamy, you should have annecdotal, theoretical, and statistical answers ready to go. You should know their ideology well so you can make annoying jokes about how ridiculous it is when applied to real life.

If you do these things, over enough time and done diplomatically enough so they don't leave you for a friend that doesn't annoy them, you can probably depeogram a red pill person.