oor simply paint each company clothing diferently (ex. you make 3 king´s bloodlines, grey, green and a red) grey for border/frontier patrols, green for elite/king´s guard, red for citie´s garrison.
What would make diferent in easy company inside a garrison? Person paint the tree of the shields diferently according to each company (in case of warriors of minas tirith)
Like this
paint the shield with same scheme cause with it you can make a bigger diference bettewn them.
Or paint them blue :)
Garrison company 1: blue clothing orange tree symbol (captain get helmet plating edges (2nd layer) around his face with orange to show a bit more elaborated pattern)
Garrison company 2: blue clothing yellow tree symbol (captain get helmet plating edges (2nd layer) around his face with yellow to show a bit more elaborated pattern)
Garrison company 3: blue clothing yellow/orange tree symbol , 50/50 (captain get helmet plating edges (2nd layer) around his face half side yellow half side orange to show a bit more elaborated pattern)
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Like this :P
as for rangers.... you could paint his chest clothing and around his mouth with diferent colour (something more royal looking but wear down with dust and time) like a regal blue with a bit of black to show a more darker and used blue from a companie´s veteran ranger)
Or paint the cloak diferently, a more expensive bow type by feathering the bow with more brown colours like if it´s made of a more expensive wood.