Pas de version en français, du coup je suis perdu dans tous les réglages.
Par exemple les textes dans les marques pages sont devenus très clair (beaucoup trop), et je n'arrive pas à trouver comment le régler car tout est en anglais !
Encore une perte de temps...

I don't know what I was expecting. I guess I thought it was going to allow me to not only set a bg image but also be able to see what the image actually is and maybe the entire navigation bar. Images only affect the tabs (windows 10). Uninstalled within 10 minutes.

I uninstalled this great extension, because it shows a white background in the tabs 'Settings', 'Add-ons manager', 'Passwords' and others

Only wanted to change active tab colour in dark theme (actually "System theme, following operating system" which is set to dark mode).
Couldn't figure out what was meant by various items I can change.
It changed more than it indicated.
Neither Undo nor Revert actually work.
Opened issue in GitHub.
Disabled add-on until it can do this 1 simple and commonly wanted tweak.
Investigating userchrome.css

Has the features it claims. But on installation makes everything ugly with no simple way to return to baseline defaults. I only wanted to change a single color, with this tool I have to manually change all the colors and then the one I actually wanted to change. I will find a different solution.

Every time I create theme I have no way of saving it. I would see it at the beginning and then when I done with my theme I can't save it.

Not bad, but could be a much better. Sadly, all your saved themes disappear once you leave the Firefox Color home editing page. And, you can't install your saved theme on another machine? When you try, it gives an error message saying the file is corrupt? The editor could be better, as well.

Really needs to be able to create a dark mode on the new tab page. That thing is blinding after using dark mode everywhere else. It feels like something so simple. Either have it match the system theme on macOS, or a simple light/dark toggle. Doesn't have to be customizable or theme matching (yet), just has to not blind me. Otherwise, really cool being able to tweak your theme, would be 5 stars without this surprisingly uncomfortable experience.

needs a darkmode option for new tabs, and the ability to upload and crop high res images for tabs, background, and new tab page.

This extension is great! Love the simple concept, UX, and tools to colourize Firefox the way I'd like!

However, I really REALLY don't like that it overrides the dark theme on the new tab page. (And why only on the new tab page? Why not also override the settings pages and stuff?) If I disable the extension, then the new tab page goes back to having dark mode.

Really, this extension should respect default behaviour by showing whichever theme my OS is set to for Firefox pages... then allowing me to choose to override that theme by selecting colours for the new tab and settings pages. That would make this extension PERFECT! :]

Most theme settings are not available!

I love it for my pc but I cant make mobile themes with it that is why I put 2 stars

It is mind blowing that your theme doesn't sync.

No way to change new tab page colour from white - Overrides dark theme and userContent.ccs so no workaround.

I was repeatedly sent to Firefox Color to this to "create my own theme" after update to 68.2esr removed my UI. Have created and saved 5 times but the theme is gone on restart. There are no instructions on how to "add" the saved theme to my themes. Is this just a toy? Or can I somehow continue to use the theme I want? Is there any info on this anywhere? Nice interface and easy to use, but a disappointing waste of time so far.

So this is the replacement of Personas Plus. Well it's not as good, that the least to say.
- On its customiser page, Personas Plus had a very convenient colour picker. Firefox Color hasn't. One star disappears.
- While the interface is efficient and easy to use, I could only use it once. Indeed, from the time I saved the theme, I couldn't go back to the interface, neither with the add-on button nor the URL. I only get a flash of that quote page and that's it. One other star disappears.
- If theme is changed via add-ons menu, where by the way saved theme from F Color isn't even listed, you can reload this saved theme by clicking the add-on button, only if all F Color tabs are closed. One other star disappears.

Maybe the problem comes from my OS which is Linux Mint 19.1 Cinnamon 64-bit.

Personas Plus has less fancy options than its successor but at least still works to apply a custom theme. I stick to it for the moment.