I think this is how it works:
RemoveColorTheme("Artemus"); // remove old one first
AddColorTheme({"Artemus","Qualitative",{"red","green","blue"},{0,.5,1}});
From the pref dialog, Graphs, double clicked a theme at the bottom to view the result of the JSL in the graphical theme editor.Them editor showing theme added by JSL
Craige