I have a question fellow Forum Users, what color of Pauldron should I use with Dark Blueish Grey Battle Armor?
I was thinking Red or Medium Blue.
(Forgive my newbness if this kind of question doesn't belong in this Forum)

use whatever color works for you.

Question are good, they help us process IMO.

For me, it would be if you plan to use it as is or if you're going to apply decals or paint. Lighter colors work best for applying things.

Of course, if you're asking whether to make a Chaos or an UltraMarine ... now that is a question only you can answer :o)

(the round pauldrons could be creatively used on the legs too ...)

Well, I'd go with red. But if you wanted to make Ultra Smurfs, there is blue battle armor.