TR3A radiator pipe color

Hi All,

Does anybody know the 'correct' color for the metal pipe connecting the upper
and lower radiator hoses on a TR3A.  I'm replacing the rubber bits and there
are a few flecks of blue-ish paint still clinging to an otherwise thoroughly
rusty pipe.  I've got to clean it up anyhow so I might as well paint it the
'right' color if there is one....probably whatever was lying around at the
factory at the time.

thanks!
Tim
Brighton, MI