While I think the coloured cuffs and facings look grand, the impression that people may get from such jackets is that the wearer acts in some sort of military capacity. Something understated and simple would, in my opinion, be the way to go if you must have different coloured facings, collar, or cuffs. I, personally, am not a fan of tartan cuffs on a black jacket; though a doublet made entirely of tartan is an attractive article of clothing!
My personal preference (which is probably not traditional) is for suit jackets with the collar in matching velvet. It doesn't stand out too much, but adds a luxurious sense of uniqueness and flair to the coat.