Changing Background Colour or Transparency

[AndyD]

Hi there,
A client supplied me their logo. It is simply text on a black background. I wondered whether there is a quick way to simply change the background colour from black to grey? I thought I knew how to do it but it seems I don't. I could simply make the logo myself, but this is now a bee in my bonnet.
The text colour is bb9222 and the new background colour 222222. I thought I could simply "convert/switch colour" somehow.
I could of course simply change the colour of the navigation bar to black, but that would be too simple.
Many thanks in advance.
Cheers,
Andrew