Thanks for your suggestions. Using page IDs in CSS is not very scalable and creates a risk point (if you change the background in a page, you have to remember to change the settings in that page AND in the CSS). Regarding the classes for the text, it’s a good idea, although in my design I have the problem that the menu is transparent, right in the center of the header, and I’d like it to have the same color and text shadow scheme as the header content; and the logo too (I change between dark and light versions to make it stand against the background and give it a drop shadow).
The simple CSS plugin is interesting, I’ll take a look.