The problem is that I want to change just one element or two from the default theme, but Firefox Color changes them all to the preexisting colors in its "Custom Color" tab, the moment I click on one and change it, so I should manually revert all the others to the original default.
This is very, very badly conceived. I should be able to change just the color of one single element, without the others being changed. I don't want to waist my time reverting all the others to the default, for which I should know what the defaults are in the first place, and I don't... BAD!
This is an extension made for those who want to play with it, not for those who just want to correct a few elements, without the fuss of having everything changed against their will, and then to have to painstakingly revert back all the colors they didn't want to change.

One easy solution would be that one of the preset themes in the "Preset Themes" tab, would be the the default one.
But of course that would not be a solution for those who already use a theme other than the default, and want to change just one color or two... The concept of this extension is wrong from the start...

PS: and You left out an important customization: the color of the sidebar itself. Hard to understand why...

4 hours picking colors. A few days later I had to reinstall the browser, export the settings to my computer. After a fresh installation, I found that there was no import button.

this is so cool :)

You cant customize the "new tab" backgraound color which can be set dark in the firefox default dark theme, so I dont see why this add-ons cant change that. I created a dark theme for myself, but cant change the white "new tab" background. pls fix.

awesome

Most of the changes don't actually work.

Je n'arrives plus à modifier le thème. La page refuse de s'afficher.

Absolutely phenomenal. There are just enough built-in templates to plant some ideas in your head, but not enough to lull you away from the actual customization settings. Color and background customization are organized into two tabs, one being the bigger/more noticeable stuff where you'll want to start new designs. The UI very clearly shows which features are edited by which widgets, and the browser itself updates very rapidly as changes are made. The second tab generally consists of much finer-detail options, like the color of mouse-over sidebar text, etc. Once you've got the hang of it, it might only take 10 or 15 minutes from start to finish to make a sweet new theme - great stress relief.

And then, even better, you can save your own themes and immediately generate shareable links to them for others to download, adopt, and customize themselves! SO RAD!! This app is like a lifesaver in Coronavirus times, when there's so much ugliness and haste - glad we can still take some time out of our rushing schedules just to glitz up our web browsers. Not everything has to be "productivity" all the time!