Just to add to Fred's post,
Is there a similar setting in Qimage?
In the image editor (open by double clicking the thumb), choose the Sel Color tab and click the file open icon.
There you'll see various options for mono prints including basic black & white which is the one to choose initially.
See attached screen shot.
This will convert the image to B&W with a filter - you then print in colour the normal way. It's best to use colour management with a printer/paper profile in use to get good greys without a colour cast.
Terry