I mean, you can always just follow reasonable contrast advice from square 1, and colorblindness won’t be an issue. It’s a pretty solved problem in the web world if people are willing to actually give a damn about it. You can have red and green text and buttons all across the screen as long as their contrast is enough that color-blind users can differentiate them.
Adding colorblind mode to a product you’ve already spent years on saying “fuck colorblind people, I don’t care about them”. Yeah, that’s not so easy.