With your coloured lines enabled in plan as per How to Enable or Disable Coloured Lines in 2020 Fusion when you print this will default to black and white as below.
When making any changes to the ppprefs.ini make sure that the Fusion application is closed prior to making any changes.
1. Click Windows Start Icon
2. Type DisplayFileLocator. This will automatically perform a Search. Click File Locator once it appears in the list.
3. Single click on PPPrefs.ini in the list.
4. A folder will automatically open, containing several .ini files. Open PPPrefs.ini.
5. Hold CTRL and F to launch search box and enter Customise
6. Under the heading [Customise] Add a new line and enter UseVectorLineRenderForPrinting = "0"
7. Save and close the ppprefs.ini
8. Launch Fusion and return to print your plan, it will now preview and print as below: