https://randoma11y.com has been updated so you can cycle through accessible combos for a particular colour. Currently supports any CSS colour name. They also added a helpful palette menu for a few common options.
Follow Una Kravets and Adam Argyle, Developer Advocates from Google, on The CSS Podcast where they gleefully breakdown complex aspects of CSS into digestible episodes covering everything from accessibility to z-index.
Nice deep dive from CSS Tricks into using dark mode in the context of websites. Did you know for example that it helps to preserve battery life for devices with OLED screen where brighter colours consume more energy?