Odd Color Names

Where do the odd color names OmniOutliner uses come from? (e.g., Gabbro, Chalk) They aren’t in any OS-X color picker that I know of, and they aren’t in the Text Style Inspector’s selection of colors for font or background. Is there a list of them somewhere? Some way to select one of them?

Both Gabbro and Chalk are from the Classic Crayon palette.