Hi JImbo,
Try to locate the printpreviw toolbar (where you can select ratio, black/white, fit, and center).
The toolbars are very confusing for new users, because users just don't notice them being added to the top toolbar area.
I added command line access for color and blackwhite modes, if you can build from source or use the latest builds:
https://github.com/LibreCAD/LibreCAD/commit/7717d5dc4edcb5817f673612b34b4fd3126085ce
JImbo wrote
About: LibreCad ----------------
Version: master
SCM Revision: 2.0.5
Compiler: GNU GCC 4.8.3
Qt Version: 4.8.6
Compiled on: Sep 11 2014
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I have a drawing with thick coloured lines (Red, 2mm) and an inserted image (shades of blue)
which prints in greyscales.
I have checked all the printer settings and options I can find but with no success.
I notice that the colours display ok on the screen in normal working but switch to B&W in Print Preview - is that a clue?