MacMillan of Rathdown wrote: “The idea that the badge of a clansman should only be rendered in monochrome really has to do with paper heraldry, where the use of coloured inks is often regarded as ‘vulgar’.”
Actually, my impression is not that it has to do with printing, but rather with the metal used for the bonnet badge.
It is not generally regarded as proper to wear an enamelled crest-badge on the balmoral, glengarry or tam o’shanter.
Of course, if one is dealing with one’s own crest, one can do whatever one wishes, but if you are wearing a clan chief’s crest it is regarded as laying claim to it if it is in colour.
Paintings and other illustrations are another matter. One can even display the chief’s full armorial bearings, if one wishes – as long as the display does not suggest that the person displaying the arms is the owner.
But I would say that wearing a tattoo is more akin to wearing a bonnet badge than to what you might display on the wall.
Regards,
Mike