Change signature colour

[Pratik]

I want to change the colour that Mozilla uses to display the signature.
I tried adding the following in my userChrome.css but it didnt work

.moz-txt-sig, .moz-signature {
        color: red;
}

.moz-txt-sig > a, .moz-signature > a {
        color: CC0033;
}

Any clues?

- Pratik