[racket] monochrome bitmaps

To clarify one point:
Is a monochrome bitmap a greyscale bitmap or a black and white bitmap?
I see from the documentation that the form (make-object bitmap% bits
width height) produces a black and white bitmap but for the form I
asked about (shown again below) subject to the restriction Matthew
described (i.e. png or xbm file format) will that produce a greyscale
bitmap or a strictly black and white bitmap?

       (make-object bitmap%
           in ;path to greyscale image files
        [ kind
          bg-color
        complain-on-failure?])

Thanks,
Harry Spier