Shared components used by Firefox and other Mozilla software, including handling of Web content; Gecko, HTML, CSS, layout, DOM, scripts, images, networking, etc. Issues with web page layout probably go here, while Firefox user interface issues belong in the Firefox product. (More info)
Unlike system colors (bug 1340696) these are not standard so I’d prefer to have them in servo/components/style rather than in rust-cssparser. With a style::values::Color enum that is similar to cssparser::Color, but has (an) additional variant(s).