For metal: If it is currently painted, youd be better off using a strong paint stripper like Rusoleum Aircraft Stripper, then using a quality self-etching primer...usually used for automotive. Then a quality spray paint.
For Plastic: If it's currently painted you *can* strip it by putting it in a bowl with Purple Power over night and then using a brass brush or similar stiff brush under running water...or in some cases spraying it with oven cleaner and putting it in a ziploc over night, then the same wash. A good paint for plastics such as Krylon Fusion can be used after roughing up the surface with 120grit.
If it's annodized aluminum, you can just rough it up and paint it. The only real way to get off anno using chemicals at your house is with a strong alkali such as in oven cleaner. In my house, it would be polished to a mirror shine and then clear-coated so that it caught all the colors surrounding it. (man, I just looked over at the happcontrols.com site and I could turn that thing into a mirror!!)

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Keep in mind that this item will have a lot of human contact and that there's nothing nastier than human touch to ruin a finish..so it may fade/wear and need to be freshened up after a while.
YMMV,
AJ