(*) These are nouns but not adjectives, one commonly add -färgad or -färgat to make an adjective/adverb out of them.
Adding ljus- or mörk- to the color means "light" and "dark", respectively, e.g. ljusgrön (light green) or mörkblå (dark blue). It is common to combine colors, e.g. rödbrun or gröngul. The first color is commonly the one thought to be most dominant. The same system is used to make colors similar to that of some well known element, e.g. sandgul (sand yellow) or havsblå (ocean blue or navy blue).