Hi Ken,Yes, evidence exists for painted helmets, both extant examples and in art. Several early 16th century great sallets retain original paint in it's entirety. At the Higgins we have an example ofa skull of one from Rhodes in worn condition retaining much of it's original paint, thought to perhaps represent a lions mane (from the lion of St. Mark) - presumably the visor would have been painted to resemble a lions face.
The early 16th century examples I cite are thought to be painted to represent mythological animals (to me they rather look like the flattish visor had been painted to represent a 'face' on a sun with rays, the rays spreading across the rest of the helmet). Several (at least 3 I can think of) late 15th century black sallets are painted all over with either badges or heraldic devices.
We also have illuminations from Spanish and other Southern European sources, from the late 13th century into the 14th cenury that show what are clearly helmets painted in heraldic colours. There are also literary references to coloured armours.
For ever painted example I can think of, in artistic representation, however, there are a half dozen polished armours, 3 or 4 that seem to be blued, and a few gilded. The majority seems to err, especially in the late middle ages, to polished white harness or blued harness, with blacked and gilded examples makeing up a small minority (in artistic representation - keep in mind however that the artist is depicting a larger percentage of wealthy people, with only a token number of footsoldiers or common men at arms - the exact opposite of most armies compositions).
I hope this helps.
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Bob R.