I have a specific website I often use (specifically, http://www.pygame.org/), which has an awful color scheme. I would like to change the color scheme of the site, but I haven't been able to find a good tool for the job.

Some basic requirements:

• It should not be universal to all websites, or affect other websites.
• I want this to be semi-automatic. I don't want to have to re-define the theme for each page of the site.
• I want to continue to access the site online (I don't want a local copy of the entire site)
• Not OS-specific (browser-specific is okay)

I am currently using Firefox, but I am also happy with Chrome.

There may be some limitations on what is able to be done automatically, as the CSS seems to be embedded in the HTML (and some also in the HTML tags). I would like to remove as much of the green as possible.

Is there an existing extension/add-on that does this?