Override CSS for Private Messaging 'compose' button style

Hi!

On Private Messaging, I'd found the provided tips to re position the 'compose' button to the left of the other buttons, but I would like to change the CSS color style of the button all around.

I did some snooping about, alas I have given up.... Could you please give me a complete sample of the CSS for the compose button style? I can take any sample and go from there to modify it and tweak it.

Many thanks!