Since the only SDs which are coloured are ROTS's, I had this idea of making them as gray as the others, just to match the rest of the saga. Make all gray, but one, u know; though I don't know which... If the chancellor's SD (the first we see in the movie would remain the only red stripped SD like making it have some distinction ala Air Force One), or Kenobi's in Utapau; as if Obi Wan was some elite-like military force; so as to match the image we've got of him in ANH (even Tarkin knows Obi Wan Kenobi).