If it was me, I would probably write a script file that would change all the colors to 7. Depending on how things are done, you would either do that by changing the color on all the layers to 7 (if objects are set to BYLAYER), or needing to select all the objects and forcing the color of the objects to 7.

That will only get top level objects, if there are items within blocks that have colors assigned by object, then you're likely looking at a lisp as the easiest way to do it, and someone else would need to step in on that one.

A lot of drawings I have run across from outside resources have a mix of BYLAYER, by individual object, and nested forced colors within blocks, so not an easy way to get it all at once.

To change all the layers to black, go to the Layer Manager, select all and change the colours to color 7. Or, if you want to retain the colours but have them print in black, create a plot-style where all the colours will print black. Again, select all the pen colors and set them to black in one go. Do a Layer Manager export as a backup to restore Layer States if a mistake is made.

Why would you want to change them? You should be able to view them with line weights in Black and White. With BricsCAD, I can do a <Ctrl><A> to select all linework and in the drawing manager I can change all the colours and/or layers. The colours are there for a reason.

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So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

If you are using viewports all you need to do is use the layer manger to set all the viewport colours to black.