White Scars Chapter Heraldry Question

[INKS]

Sometimes they seem to have red rimmed pauldrons and sometimes not. Can't figure out when to have this and when not too. I thought it was Sgts, but that doesn't seem to be the case all the time.

[lansalt]

30k - Every WS has red trimmed pauldrons (besides a few specialists)

40k - Old firsborn, veterans, and officers. Nprmal primaris marines don't have red trim.

[Sgt.Sangha]

Infact back in the day they also had black squad symbol markings for 40k and all red for 30k 

 

I paint all my shoulder trims in red, just to add some more contrast, Iv also been experimenting with adding either a black or red solid band vertically on the right Pad of Sgt models or squad leaders. That allows me to open up and use some the 30K decals or create my own feel for my version of the white scars