- Download the Stylus extension (custom CSS)
- Download the Tampermonkey extension (custom JS)
- In Stylus, create a style for twitch.tv, and copy the stylus_chrome.css lines into it, and click save
- In Tampermonkey, "Create a new script..." and copy the tampermonkey_chrome.js lines into it, and click File->Save (in Tampermonkey on the top left)
- Refresh the twitch page, and chat should now look a lot better.