There are lots of color resources on the web, for artists, designers and others, but an often overlooked one is Wikipedia, the venerable user-edited online encyclopedia.
Whatever you may say about the reliability of the information on Wikipedia (or from Britannica, or any other single resource, for that matter), I rarely consider a source like Wikipedia a place to end a search, but, like Google, a place to begin one.
Though not specifically an artist’s resource, Wikipedia’s color related articles are numerous and varied.
You might find it interesting to start with their “List of Colors“. The list includes a lot of non-artist colors, like “British Racing Green” and “Psychedelic Purple”, but the familiar artist pigments are there too. Links for those lead to articles with information about the pigment, including source materials, history, chemical composition, lightfastness, typical use, hazardous qualities, color system numbers and sometimes more.
Some are grouped; Cadmium Yellow, Cadmium Orange and Cadmium Red all lead to a single entry for “Cadmium pigments“, but some have more extensive and interesting listings, like the history behind Ultramarine.
Though hardly an exhaustive resource on color for artists, it does seem a valuable resource to add to your virtual palette.