AutoCAD Release 11 only supports 15 pens. The Autodesk Device Interface
(ADI) specification currently supports 128, but I don't know how they are
mapped. The ADI spec will probably support 256 pens in Release 12.
If you want an ADI driver, please ask the hardware manufacturer. The ADI
spec was written so that hardware vendors could write the interface between
their new (and old) devices and AutoCAD. We just can't keep up with the
hundreds of new video boards, digitizers, plotters and printers being
manufacturered, all with different ways of doing the same thing. We do try
to provide drivers for the most popular hardware at the time of release.