One point I’m always at pains to make to my web design students is that accessibility isn’t an add-on to your design. You have to be as inclusive as possible from the outset.
Anyway, I thought this was a great article on designing for people with colour blindness:
https://www.smashingmagazine.com/2024/02/designing-for-colorblindness/?ref=web-design-weekly.com
One thing the article omits is the fantastic accessibility in Firefox Developer Edition.
Perhaps these tools aren't well known — they're in the web inspector. It’s a great way to test your site.