I have seen that HTML signature in thunderbird will be shown as grey color. Even though my signature is not in grey color the default grey color will be shown. How to resolve this issue?
You can edit the signature in HTML by ticking the "use HTML" checkbox in the Signature Text box.
Then in the signature box type something like
The other answer didn't work for me. Thunderbird displays the signature in grey regardless, even when the email is sent out (at first i thought it was just at the editing stage).
1) find your profile folder in ~/.mozilla-thunderbird (it is a hidden folder)
2) create a folder called "chrome" inside of it
3) inside the "chrome" folder create an empty file called "userContent.css"
4) edit "userContent.css" in a text editor and add these lines:
5) restart thunderbird