I don't think the color would make much difference. I would choose white, but if it stays in the pond...it's going to discolor anyhow. With that said, I would use a box (or cylindrical) cage instead made from wire cloth just hanging from a rope off the dock if it is something that will be pulled out often. I have a box cage made from plastic coated wire mesh and like it alot for that purpose. That barrel cage is going to be a booger to get in and out of the water and will be as much, if not more, work than hog ringing some wire mesh together. They drilled alot of holes in it, but it will take a fair amount of time while pulling it out of the water to drain enough to be light enough to handle... a wire cage will not have this problem. The barrel cage would work better and last longer if it were a permanent installation in the water and you used a long-ish net to retrieve the bait. At that point I would forego the flotation noodle and just mount it to the dock.
