As alemanda said, change the pen set of your drawings in the layout to use black pens.
Or in the DOCUMENT OPTIONS for the PDF in publisher, you can choose to save PDF with colour, black & white or greyscale.
Barry.
One of the forum moderators. Versions 6.5 to 27 i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10 Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11