Impossible to change the color of visited links in Tor Browser
Changing the color of visited links (for example, from blue to purple) is a core feature of web navigation since it's origin. It helps users navigate websites by making it easier to understand where they have been already and where they can go.
In 2011, it was qualified as top 3 mistake in web design by UX guru Jakob Nielsen:
In Tor Browser 8.0.6, visited links don't change color. I tried this on several websites: