aquarium sealant should not harm the paint. I don't know about paint fade in the sun over long periods of time.
having used aquarium sealant in the past to secure carbon pieces to bikes (swingarm and frame covers on S1000RRs), I do have a question - has anyone ever REMOVED these sliders? I can't think of a way to do it that wouldn't damage the tank - that sealant is pretty tough stuff.