Simple addon. It's very intuitive and easy to use.
For those who complain about the impossibility to save your customonization (for another device or anything else) , it's because of security. It's quite complicated for new users to deal with that.
BUT THERE IS AN ALTERNATIVE : just save or bookmark the URL when you set your colors (it changes after ANY modification you make). After that, you just need to revisit your saved URL to reinstall your custom colors.

Excellent add-on. People with color perception issues can fine tune FF to their needs.

Thanks to this, it looks like hatsune miku! <333333

This is an awesome addition. It's so hard to find a specific colour theme I like, but now I can choose exactly the colours I want. Brilliant extension.

ruined my browsing experience, might have to go back to chrome because wtf is this??? don't know how to fix this glitch uninstalled app, uninstalled & reinstalled firefox...still the same

It's a great option - but too hard to find where to make changes to it!