Signature display color

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This article was written for Thunderbird but also applies to Mozilla Suite / SeaMonkey (though some menu sequences may differ).

By default, Thunderbird displays the signature text, and the signature separator ("-- ") above it, in the color gray. If you wish to change this to another color, insert the following into your "userContent.css" file.

 * Change display color of text and links in signature
.moz-txt-sig, .moz-signature {
  color: black !important;
.moz-txt-sig > a, .moz-signature > a {
  color: blue !important;

The above example will make the signature text black and links in signatures blue. You can use other colors as desired.


  • This changes only the way that signatures are displayed in Thunderbird and will not affect the color of any signatures that you use with outgoing messages. However, recipients who use Thunderbird normally see gray signatures unless they have changed the setting too. Other mail clients might do similar things.
  • If you use an HTML signature file, it can specify its own color for the text but not for the signature separator ("-- ").

Changes with Thunderbird 22.0 beta and SeaMonkey 2.19

Thunderbird 22.0 beta 1 (becoming effective with the 24.0 release) extends the display-color preferences UI to match that of Firefox. As a consequence, signature and its link colors will no longer be constants but deemphasized by opacity. For SeaMonkey, this will become effective with its 2.19 release. Thus, the respective userContent.css rules replacing the code mentioned above should be:

.moz-txt-sig, .moz-signature {
  opacity: inherit !important;

This will also be needed if you specify a "color:" along with it. Also, there is no longer a separate rule for links, the opacity applies to the selected colors for both of those.

Outgoing messages

To ensure that your own signature is displayed without opacity in messages others receive from you, add the following code to your signature and check the "Use HTML" box:

.moz-txt-sig, .moz-signature {
  opacity: inherit !important;

Note: The recipient may use an older version of Thunderbird/SeaMonkey or a 3rd-party theme which didn't make the transition to the opacity style. Thus, you can consider adding the color-specific override code between the <style> tags as well.

External links

See also