Hi Dean,
Well, I'm not an AutoCAD expert, but upon my experience, in case of importing splines from a .dwg file, its Color is used for generating the 3ds max Material ID. If you want to avoid the Edit Spline modifier step - assigning the Red color to such spline (layer) should result in ID 1 / Yellow as ID2 (as the Red color should be indexed 1 (Yellow 2) in AutoCAD). Hope that helps.
Best regars,