Stay with Black.
Previous owners of our Jayco thought black looked awful so had "somebody" paint it white on their travels. White rusted and flaked off to rust and black. I cleaned it up and painted black rustoleum with a brush. Actually looks better (at least to me) than it did but damage is done. It's all pitted, so why fuss about brush marks?
Don't store Sewer Hose in the bumper. It'll rust through prematurely. Also, spare tire mount on the bumper will tear the thin steel at the bracket welds.
A new square tube steel "bumper" is inexpensive, but it doesn't have brackets installed. By the time you get brackets and have them welded on, it becomes quite a little more costly. I say "bumper" because it might deflect a bicycle. Any hit from a vehicle will cave it in. Probably enough to offer a little protection to the even more fragile coach body, though. Like in cases of easing back into a post in a campground. Not much more...