The Clergy Tartan White /Blue/ Black;
Black was worn by Clergy because it used to be the cheapest cloth, and reflected the simple lifestyle. White for purity of service, blue, colour of humility. The Clergy ideal...
Of course, this is a modern interpretation. Colour symbolism in tartans is a relatively recent thing -- you see it most in district tartans where the colours symbolise a different aspect of a state/province/district.

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