There is a type defined, Autodesk.AutoCAD.Colors.
This type has some shared methods, like 'FromColorIndex(colorMethod,colorIndex)' where color method is the enum type ColorMethod which defines among others 'ByAci', and colorIndex is of numerical type Short.
This method returns a Autodesk.AutoCAD.Color object.
The Autodesk.AutoCAD.Color type defines Red,Blue,Green as byte.