Metalic paint may make a difference if it creates a short across an
insulator, or creates a shield on the outside of the fiberglass tube
that protects a VHF/UHF antenna.
But the "metalic" paints I've seen aren't actually conductive,
they just have sparkles of metal in them. It might produce
some dielectric loading effects in certain cases that would
shift the resonant frequency slightly, but otherwise I doubt
it would make much difference.
Probably isn't the best choice for making the antenna less
obvious, but I don't know the background color scheme of
your house...