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, for example, Firefox → menu 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.
Best Answer
Firefox
You can do this by editing (or creating if it is not there) the file
userContent.css
. Its location depends on the platform (the parent folder can also be found in menu Help → "Troubleshooting Information" → section "Application Basics" → field "Profile Directory" ("Profile Folder" on Windows)):Linux
$HOME/.mozilla/firefox/[xyz].default-release/chrome/userContent.css
Windows
Depending on the Windows version and other configuration,
userContent.css
is in one of the following folders:C:\Documents and Settings\[username]\Application Data\Mozilla\Firefox\Profiles\[xyz].default\chrome
.C:\Users\[username]\AppData\Roaming\Mozilla\Firefox\Profiles\[xyz].default\chrome
(more generally, it is%APPDATA%\Mozilla\Firefox\Profiles\[xyz].default\chrome
).Common for Linux and Windows
You may have to create the
chrome
subdirectory and the fileuserContent.css
.Add these lines to that file to change the colors (obviously, you can change the actual colors used to whatever you prefer - e.g. using Paletton Live Colorizer):
In most cases Firefox has to be restarted before it takes effect.
Also, for later versions of Firefox (69 and later), check that toolkit.legacyUserProfileCustomizations.stylesheet in about:config is true. In some cases it is automatically set to true when file
userContent.css
is created, but that is not always the case.Chrome
You can do the same for Chrome by editing
$HOME/.config/google-chrome/Default/User\ StyleSheets/Custom.css
which on Windows, is located at%USERPROFILE%\AppData\Local\Google\Chrome\User Data\Default\User StyleSheets\Custom.css
.