Thunderbird struggles with dark Plasma theme colours

Does anyone happen to know WHICH line in /usr/share/themes/Breath-Dark/gtk-3.0/gtk.css is responsible for causing Thunderbird's white-on-almost-white misbehaviour like this please?:


Light theme colours do not suffer this bad contrast error:


I have scrolled right through the css, but it is hopeless when i don't know enough of the jargon & concepts underpinning GTK3 theming to be able to find what i need to edit.

Every dark GTK3 theme i have tried, both shipped standard with Manjaro KDE, & also maybe a dozen i downloaded & tested, suffer this identical error. Surely there must be a specific line in that css controlling this?

Note: I probably won't be able to stay at my pc any longer tonight [currently my 21:00], so if anyone does reply please don't be upset if i don't see it & reply til sometime tomorrow my time.

not really a helpful comment from my side, but recently I noticed a similar problem with Inkscape on my wife's Plasma install. As a workaround, we changed the GTK application style to Adwaita.

I just had to make a test, i don't use Thunderbird nor any thunder devices ... etc :stuck_out_tongue: but i have a totally different look ... still inconsistent and odd, but different
Made the test with all the GTK themes i have (and there are quite a few) with or without the option to Prefer Dark GTK3 Theme in Gnome Application Style settings ... almost all behave the same, except Adapta-Nokto-Eta-Breath

and Arc Dark (my favorite one :slight_smile: )

First it should be clear that this is not a KDE or KDE color/theme issue. Thunderbird is GTK so it is getting its cues from there [System Settings>Application Style>Gnome Application Style (GTK)]

For me I cannot reproduce.

Using Adapta-Nokto-Breath in both GTK2 and GTK3 fields and marking 'Prefer Dark GTK3 Theme'


I know this. Hence my OP explicitly stated:

I proved to myself yesterday during my investigations that this css controls TB's aesthetics, by finding a line pertaining to background colour, temporarily replacing its dark grey / light black colour with a shocking pink [no danger of me not noticing it, ha], restarting TB, & seeing the visual confirmation of the change. However as i also said in my OP, i have been unable to identify the specific line in the css [amongst its 3,774 lines] controlling the actual part of TB that is problematic, per my picture.

I am happy for you if that is so, but with respect your picture does not support your claim. If you look again at my OP's dark-theme picture you can see that my calendar also shows perfectly fine. That was never the issue. My problem arises once, in that popup calendar, i click on the Year field to select a different year. As my pictures show, the resultant dropdown menu is unreadable with a dark theme, but ok with a light theme.

For me, choosing ‘Prefer Dark GTK3 Theme’, or not, makes no difference at all to the problem.

Thank you for testing, but the difference between yours & mine is simply astonishing.


I'm using gnome but have faced similar issues with all dark themes tested with thunderbird (I could not read emails from some of my colleagues), qgis (some options were white on white), etc. So I've sadly switched back to standard light themes.

Thank you.

I've made a minor break-through. It is brutal, clumsy, inelegant, & arbitrary... but it does now give me an ongoing capability to still use a dark GTK3 colour [in my Plasma Settings] AND continue to access the full functionality of Thunderbird without that useless white-on-white in the popup calendar dropdown menus, whilst still providing "acceptable" contrast of this new font colour everywhere else in the TB UI against the theme's dark background.

This is my workaround brute-force method:

  1. Copied /usr/share/themes/Breath-Dark to /home/kdemeoz/.themes/Breath-Dark_kdemeoz-GTK3.
  2. Backed-up /home/kdemeoz/.themes/Breath-Dark_kdemeoz-GTK3/gtk-3.0/gtk.css for emergency recovery.
  3. Edited /home/kdemeoz/.themes/Breath-Dark_kdemeoz-GTK3/gtk-3.0/gtk.css; searched for EVERY instance of white, bulk-replaced with #aaaaff.

I verified with Pamac & Firefox, as representative other GTK3 programs installed, that this new font colour is viable in these as well.

As an initial proof-of-concept, i had replaced all white with vivid-yellow #ffff00 [excellent contrast against dark background, hopelessly unusable contrast still in those dropdown menus], & then #ff00ff, yielding this ghastly:


So, certainly there is one line somewhere within that big css, which if i could just find it & change only its white, i would have the perfect solution. Maybe one rainy day i shall repeat my search for it, but until then, my brutal current workaround shall have to suffice. Haha.

I followed another approach, which is not theme-based but Thunderbird-based.
You can test it and see if it fits your needs.

  1. Close TB and create a folder named “chrome” in your TB profile.
  2. Create a file named “userChrome.css” in the “chrome” folder.
  3. Add the following to the newly created file “userChrome.css”:

/* Thunderbird styling for Breath-Dark theme. */

/* Datepicker */
.datepicker-text-class {
background-color: #292f34;
border: 1px solid;
border-color: #5f6367;

/* Year popupmenu */
.minimonth-list {
background-color: #292f34;
color: #f1f2f2;

.minimonth-list:hover {
background-color: #780bf7! important;

/* Year popupmenu up-down buttons */
.autorepeatbutton-up, .autorepeatbutton-down {
background-color: #292f34;

Open TB to see the modifications. You can change the colors in the css file according to your liking for a better result.

It's not a very elegant approach, since the modifications will apply to TB regardless of the theme you are using. That means, if you change to a different theme (a light one), the content of the css file has to be commented out or modified to match the colors of the new theme. :thinking:


Hi Bill

Thank you so much. This was very very clever of you, & it completely solves my problem. Your way is vastly more elegant & sophisticated than my brute-force way, despite your comment.

How did you know the specific Thunderbird item names to use?


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You're welcome kdemeoz, I'm glad that it worked and you liked the result! :slightly_smiling_face:

To find the classes that needed modification, I used the “Developer Toolbox” option in TB (Tools > Developer Tools) and the Thunderbird DXR found here (there is a very nice search function in the DXR that helped me a lot). And a lot of testing in TB!


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You guys are really going for it!
Another (very lazy) option is to use a thunderbird dark theme: and install TT Deep dark.
Of course it will not match exactly your theme, and you might not like it.
Only for the lazy!

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Hi! Oddly enough I don't have this problem. I'm using Adwaita Dark and my Thunderbird is beautifully rendered in a dark theme ; here are the settings I used. I know it's not Breath-Dark, but it's good enough for me.


Hi BC - thanks for testing. Your apparent result is certainly different to mine... the standard Adwaita Dark GTK3 Theme was one of my very early tests, which i rejected, coz it does this:


I find it amazing & inexplicable that apparently your TB Event & Task popup calendar dropdown year selector does not blank out the years like my tests' OP image above, & again now [if i revert to Adwaita Dark GTK3 Theme] do. Had it worked for me i'd not have needed all my testing, & ultimately the success of @bill_t's workaround above.

Pls could you confirm that you are explicitly talking about the same thing i am? It is not a generic whole-TB rendering problem with dark themes, it is specifically Event & Task popup calendar dropdown year selector.

Hi kdemeoz,

I can confirm I don't have this issue in Tasks or Calendars, everything renders correctly, white text, dark background. I'm running an nVidia GTX970 with the nvidia drivers, I wonder if it's something specific to rendering perhaps?

I'll try another theme when I get a chance and see if I can replicate your issue.

Also checked: I set Breath Dark colors, Breeze application look, then Breath Dark for Gtk 2 and 3. Here is the result:


Many thanks for your testing & reply. Yes now i also wonder if it's a weird rendering outcome caused by my use of the integrated Intel GPU... i do not use any external [eg, NVidia] GPU card. I do still find that a hard hypothesis to swallow, but so far no better hypothesis has survived all my tests per this thread. Weird.

Thanks for your testing & reply. I replicated your stated config exactly [despite my abject disdain for Breeze iconography; ugh] then logged out/in of the VM to guarantee no artefacts from its usual aesthetics settings, launched TB... & saw yet again the white font on almost-white background problem per my OP image & my preceding-post's image. Weird^2.

Note: Despite the fact that i am doing these recent tests only in a KDE VM [for lazy convenience], previously i already tested this problem to death in my real systems, prior to creating this thread.

I hoped you noticed I haven't said anything about desktop theme which is irrelevant in that matter. Some may confuse color for theme. Color setting is usually the one we tend to forget the most and when it's set wrong, we can get those mismatched white on white or black on black areas.

I noticed this especially with Kvantum. On surface, when using Kvantum, changing colors don't do anything, but some areas are affected and we forget adjusting colors we get that white/white and black/black effect somewhere.

I'm not saying that this is the cause in your case. However it looks that it for most people this seems to render ok (well, the year stripe still is off) but somehow, you get "the bug" on real and virtual system, while others not, so that suggest you have to be doing something different. What is this "something" is a good question :wink: .

EDIT: Or maybe desktop theme somehow does have a say in this? Maybe that's the piece that is different? Hmm..

Despite the fact that [i thought] the general KDE System Settings Colour settings are supposed to be wholly independent of the KDE GTK3 Theme, i have a growing suspicion that in fact there might be some internal "sneak circuit" causing bleed-through. My KDE Colours are definitely customised/personalised [ie, on balance of probability ergo different to all other Manjaroos' who have kindly posted herein], & though all my efforts to pin the root cause down so far have failed, i will not be surprised if one day i find some arcane conflict between my colours & the GTK3 Theme that is applied to TB.

Of course, atm i cannot prove any of that conjecture, & it might only be a steaming pile of donkey-doodoos...

The new TB has a dark theme!

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