Basically, it is a matter of good taste, or aesthetics. To anyone with a keen eye for what looks right, a tartan (any tartan) can only be set-off, or shown to advantage, by a plain, self-coloured shirt, jacket or sweater - and the colour should compliment, match or be a paler version of one of the colours in the tartan. Preferably, one of the less obvious colours. The kilt itself should be the focus of attention and should not have to vie with anything else.
Hamish,

That was the point I was making -- my glen plaid shirt that I wear is a very pale blue with a very light pattern; the pale blue matches a line of pale blue running through my kilt, and you can barely see the pattern -- the pattern does not interfere with the tartan in the kilt. I'm not suggesting that anyone wear an extremely loud pattern.

If you look at the picture in my gallery of my day attire, you can't even tell that the shirt is glen plaid -- it looks like a light blue shirt.

I can't find a photo of him at the moment, but I know that HRH Prince Charles does wear a tattersall shirt with a regimental tie with his kilt on occasion, and I can't imagine anyone telling him he is wrong! :mrgreen:

This has become a "tempest in a tea cup", and I apologise for my part in starting it. I am not attempting to ignore tradition; far from it. I respect your opinions greatly, Hamish, as you are the epitome of a gentleman, and I would not want you to think less of me.

Cheers,

T.