Some people who suffer protanomaly can hardly distinguish red text from black text on computer screens. Many web pages like AskUbuntu.com show visited and unvisited text links in red'ish colors. That reduces usability drastically for those affected.
How do I change the color of un/visited text links of Firefox and Chrome on Windows and Linux to classic blue'ish colors, thus making the web usable for people who suffer protanomaly?
The settings of Firefox and Chrome offer to override fonts and colors, e.g Firefox -> Edit -> Preferences -> Content -> Colors... -> untick Allow pages to choose their own colors. But that changes all fonts and all colors of every element. That's not desired; just the color of text links, no more no less.