I've tried a method using a userContent.css file that applies a custom background color to the message composer (and for received mail) for plain text messages, but not for html-format mail. Create a folder named chrome in the profile folder, then use a text editor to create a userContent.css file in the chrome folder with this content: @namespace url(http://www.w3.org/1999/xhtml);

body {

  background-color: #C0E7F3;

} Choose any color you like (the example is light blue). Perhaps someone can explain why it doesn't work for html.

You can achieve the same result by changing the background color in Tools/Options/Display/Formatting/Fonts & Colors/Colors.

It doesn't seem to work, it changes the plain text messages background of received messages, but not my compose message window background.

Is it working for you?

If your default format is html for composing messages, hold Shift when you click Write or Reply to switch to the plain-text composer.

sfhowes said

If your default format is html for composing messages, hold Shift when you click Write or Reply to switch to the plain-text composer.

Ok I see how that works. I have to compose a plain-text email. So your setting seems to have the same effects as changing

user_pref("browser.display.background_color", "#DADADA");

in the prefs.js, doesn't it?

How can I change my default to plain-text?

Yes, see the last paragraph of my first reply; the color display option is the same as changing browser.display.background_color in Config. editor.

The composer format is set in Tools/Account Settings, Composition & Addressing for an account, 'Compose messages in HTML format'.

I can get sfhowes said

I've tried a method using a userContent.css file that applies a custom background color to the message composer (and for received mail) for plain text messages, but not for html-format mail. Create a folder named chrome in the profile folder, then use a text editor to create a userContent.css file in the chrome folder with this content: @namespace url(http://www.w3.org/1999/xhtml); body { background-color: #C0E7F3; } Choose any color you like (the example is light blue). Perhaps someone can explain why it doesn't work for html. You can achieve the same result by changing the background color in Tools/Options/Display/Formatting/Fonts & Colors/Colors.

I can only get this to work by changing "Tools/Options/Display/Formatting/Fonts & Colors/Colors."

Thunderbird will not pick up the userChrome.css file content.

Has anyone figured out how to change the color of the compose window for html?

Note that the above css file is userContent.css, not userChrome.css.

The background color for composing html messages is set in Tools/Options/Composition/General/HTML/Background Color, or the preference msgcompose.background_color in Config. editor.

Wow, thank you!

Do you have any idea if changing msgcompose.background_color in Config. editor leads to the email background being colored when others receive it? (I don't want it to be)

I tried sending a test to a gmail account and it had a white background which is great. Hopefully, it works across the board. I'm using a dark background with light text for my own viewing but I want other people to just see normal black text on white background when they receive my emails.

The background color can be changed for plain text messages as you see them (Display options), but this color isn't transmitted to recipients. That's the issue of the original post. Changing the background color in the Composition options does affect what is embedded in a message, but it may or may not be seen by the recipient, just like with custom fonts, if the recipient has defined a certain type of display, e.g. plain text instead of html, or doesn't allow the colors or fonts to be overridden (see Tools/Options/Display/Formatting/Fonts & Colors).

Even if you set the transmitted default as black on white for composed mail, you can still make a different choice for how it's displayed on your system. And the recipient may also choose something different from black on white.

That's exactly why I couldn't rely on the HTML background color, people were complaining that my emails had a grey background. It's really annoying because now I'm forced to compose emails in plain text. I don't understand why there is no solution for such a simple problem. TB could just change the HTML color background after you hit send.

It's almost comical how difficult this is. I created a great dark theme for Gmail (https://lioncx.com/2018/10/21/gmail-dark-theme-2019/), but I've decided I don't want to use Google products anymore.

I haven't found anything that can touch their interface, although Thunderbird is not bad. But this compose window issue is annoying. I don't like being stuck with plain text.

The only other thing I've found that's a possibility is Mailbird. They do have an integrated dark theme and their sort of clunking along in the wake of Google's UI. I may end up using their product instead, just so I can have the rich text editor.

Aha! :)

Go to Options > Display > Fonts and Colors > Colors and set the colors you want.

Then, on that same screen, set "Override the colors specified by the content with my selection above:" to "Always".

No need for any custom css.

Problem solved!!!

Edit: I also discovered how to set a universal shortcut for composing email from anywhere in Windows. Very convenient. See bottom of this page: https://lioncx.com/2019/07/26/gmail-alternative/

Does this solution apply to HTML and it's only visible when you compose an HTML message? Are you sure?

Pretty sure. If you want to contact me, I’ll send you a test email: https://lioncx.com/contact-us/