If you are printing a colored print in black and white:

Look in the Print dialog box at the bottom - Additional Options - Print Style Table.

Mine is set to monochrome.ctb and prints in black and white. All lines print the same.

Also, they are located in Program Files - Dassault Systemes, Default Files, Print Styles.

Other Styles print differently and you'd have to set them for your printer.

I have tried this now, but yellow lines are still appearing blurred.
Any other suggestions, please?

What are your settings in the Additional Options?
I have - Use assigned Print Styles checked & Print Quality: Normal.

Make sure your Yellow Layer is color 2 and not 50 or 51.
Go To Options - System Options - Printing - Print Style File Location and find where your files are located.
Go To the location.
Double Click the monochrome.ctb - Table view - Color 2 - dithering-on, convert to grayscale-off.

Thank you, I will try this as soon as possible