Sailing here too, and it was my job for 40 years, I just find for north one yellow is too low from sea level and for south one it's black
Edit: example noth one
Very nice, for the black/yellow buyos, in international code you have yellow/black, yellow/black/yellow, black/yellow/black and black/yellow when you go from top to bottom to make north, east, south and west buyos
You can make the mod not necessary by modifying the mission file:
1-Make and save a mission with template
2-Open the .miz file with WinRaR (for example)
3-Open the file "mission" with Notepad++ (note the text editor from Windows)
4-Erase the lines from ["requiredModules"] to --end of ["requiredModules"] (see screenshot)
5-Save in Notepad++, save in WinRaR, you can now open the .miz in mission editor
6-Erase the units from the mod you have not
7-Save as new template
For those who want these buoys I share them, I add a "Channel" buoy with default textures to have it as original one in "Static objects". To have liveries choose them in "Ships". Copy/paste "buoy_navigation" folder in "Liveries" folder of the mod Civilian Assets Pack Navy
Link: https://drive.google.com/file/d/1-eApIHAHQmv-86qjXWOR9A4kdGFE6G2x/view?usp=sharing
Installation.txt