So you want to take you multi-colored drawing and plot it in just black and white, but how?  This post is a direct result of a question I received from an attendee on the See the Difference with AutoCAD 2010 Tour in October.
In AutoCAD when you go to the Plot command and enter the Plot dialog expand the Plot dialog.
Select the Monochrome plot style (ctb or stb). Now select Apply to the Layout and preview or Plot and you should should be good to go.
Between the Lines - Autodesk blog by Shaan Hurley