I created a 3D solid model in colour and print it in viewport paper space. Print setting is monochrome by default. Text, dimensions printed as black and white but the 3D solid still printed in colour.
 
Is anyone know any setting can do the job?
 
Regards
 
Teddy
 
 

Did you specify a True Color for the color of the layer the solid is on by any chance?Did you double check your monochrome plot style to verify that all layer colors are set to black?

I give a simply try by drawing a box with colour RED (index color 1).
create viewport in paper space and plot by monochrome plot style (default by acad). I check the plot style, they are set as black colour.
 
Print in monochrome is ok until I change the visual style to realistic or conceptual, the object stayed in colour.
 
Any advise?
 
 

I tried your little experiment and both plots printed in black.  The only difference was that when I previewed the one that was set to the Realistic visual style the box remained red which is what I expected. 

I still can't print B&W by this method.
 
However, I find I can use shad plot and changes to shades of gray when plot. It works fine to produce a grey scale printout.
 
Thanks for your help.