Why do the envelope lines and item ID show up in color when you plot to pdf or print?

Why do the envelope lines and item ID show up in color when you plot to pdf or print?

This problem can occur if you use a monochrome.ctb plot style instead of monochrome.stb plot style.

Refer this document to configure the plot style, and then select monochrome.stb plot

style while printing or plotting/exporting to pdf.

HyDraw-CAD-Configure-Monochrome-Plot-Style.pdf