How can I change link colors in Firefox and Chrome, but leave all other colors and fonts as they are?

Question

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.

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 → "More Troubleshooting Information" → section "Application Basics" → field "Profile Directory" ("Profile Folder" on Windows). An alternative way to using the menus to open the Troubleshooting Information page is the "URL" about:support. To find the location for other than the current active profile, use the "URL" about:profiles (will open the "About Profiles" page) and press button "Open Directory" in the "Root Directory" row for a profile):

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 file userContent.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):

a { color: #333388!important; }  /* Unvisited link color */

a:visited { color: #333340!important; }  /* Visited link color */

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.

In most cases Firefox has to be restarted before it takes effect (or rather, the profile in which these settings have been changed. There is a current active profile, but if more than one is in active use, this has to be considered).

Note that both file userContent.css and setting toolkit.legacyUserProfileCustomizations.stylesheet are per profile (they are not global settings), so if using more than one profile it must be copied to the sub folder in the particular profile folder, and set in each profile, respectively. The same goes for restarting - close the corresponding window and in the case of a non-default profile, open it from the default profile (e.g., from "URL" about:profiles).

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.

Comments

[Peter Mortensen]

Related (to the accepted answer): How can I override the CSS of a site in Firefox with userContent.css?

[Peter Mortensen]

Similar for Thunderbird (using the same files, for font size): How can I change the font size of a Thunderbird thread list on a Mac?

[Peter Mortensen]

Other base setup: Firefox: non-Vimperator way to do mouseless browsing

[terdon]

@JoBo you're quite right, I thought it only applied to the links. I am trying to figure out how to do this via CSS, it should be possible. As for the link, it is an answer when it is only part of a larger answer and when the link is to a resource that does what you need. Link only answers refer to, well, link only answers.

[Johannes Kohnen]

I am looking for a comprehensive, to the point answer that let's others who suffer the same benefit as easy as possible without further searching/reading and without installing any add ons.

[terdon]

@JoBo will that do?

[Johannes Kohnen]

Not quite, but it's getting there. blue and green aren't the "classic blue'ish" colors. I don't know what to use here. I am terrible at design stuff. Sth. like rgb(16, 134, 164) or so? The correct Windows path is %USERPROFILE%\AppData\Local\Google\Chrome\User Data\Default\User StyleSheets\Custom.css.

[terdon]

@JoBo I don't know what colors you want, that's up to you. Have a look at sites like colorschemedesigner.com, they give your the HEX code (RGB) for each color you chose. CSS can understand those, so for example, to make your links red, you would use color: #FF0000. And the path you gave is exactly the same one I had apart from the capitalization which should make no difference in the Windows world right?

[Johannes Kohnen]

Thanks! How does it change visited links? The issue is not how to distinguish visited from unvisited links, but to distinguish links from normal text.

[Peter Mortensen]

The name of the last folder seems to have changed, -[number] is appended: [xyz].default-[number]. Sample: ... \Application Data\Mozilla\Firefox\Profiles\yynxpuma.default-1439568940109

[Peter Mortensen]

+1: This worked as advertised when tried with Firefox 45.0.2 (current as of 2016-04-23), but only after restarting Firefox. Can you add some of this information to your answer?

[terdon]

@PeterMortensen would you mind doing it instead? I don't have access to a Windows machine so I can't test it and I'm not entirely sure what I should add.

[Peter Mortensen]

@Johannes: I can not confirm that the correct Windows path is the ...Local... one. After a long series of controlled experiments I can conclude that %APPDATA%\Mozilla\Firefox\Profiles\[xyz].default\chrome works perfectly fine (when using "/* */ as comment characters"). Or perhaps that was for a different context (the file name is different)?

[Amy Pellegrini]

This seems like an unfair hard requirement on behalf of FF, it is not how I expect CSS to work according to specs. I wonder if these rules can be overriden without an additional stylesheet just to please browsers... like the old days of IE6/7/8/9/11

[terdon]

@AmyPellegrini hmm? What requirement? What isn't how you would expect CSS to work?

[Amy Pellegrini]

I'm using a brand new FF installation, and it comes with a PreferenceStylesheet with style rules that override my application styles. I never set such a thing, but now I find in the need to override those styles, or the get around what this PreferenceStylesheet is about.

[terdon]

@AmyPellegrini not sure what you mean, but it sounds like you want to contact the firefox devs. I'm just the messenger :).

[Peter Mortensen]

I can confirm that the toolkit.legacyUserProfileCustomizations.stylesheet part is necessary. On an updated (as far as that is possible) Ubuntu 18.04 (Bionic Beaver) system and an updated/current version of Firefox (76.0.1) it was set to false. After setting it to true and restarting Firefox, it worked.

[Peter Mortensen]

The same for a Ubuntu MATE 20.04 (Focal Fossa) system.

[terdon]

@PeterMortensen I rolled back your edit because I don't think a discussion about a specific site (or specific styles) is relevant. This answer is already quite long, let's not make it longer.