But how does rendering it in B&W represent the fact that this is the clansman's badge? Doesn't encircling the crest withint the belt and buckle bearing the motto serve that function?
Rendering it in B/W is meant to depict the badge in metal, silver coloured metal in heraldry is depicted as white. I don't think Lyon Court would be saying it should always be depicted this way unless it was. After all Lyon is the one that dictates the rules for helraldry.

The only way a clansman can show allegiance to his Chief is the wearing of the clansman's badge in a belt and buckle and that is only as a courtesy even to his own sons.