I would probably use those colors as a trim to the arm and wrist segments of the armor.
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The wrist on the power arm might look nice in white. And the head, since sergeants usually have white helmets with Red Scorpions... especially since the head resembles a power armor head a lot. But I'm not that much into fluff, so I don't know how if that's fluff accurate (aside from if you even want to make it somewhat accurate)
As for red I'm a bit clueless, but you don't see a lot of red besides the chapter icon on Red scorpions.
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