Jock and Hamish,
I wasn't sure myself, but i took advice, and we were perfectly fine.There a reasonable scattering of morning dress, but all with black top hats:although that may have been due to the various Gentlemen attendants, but what surprised me was the number of rather ordinary suits, and even brown ones... ( never brown in town , came to mind) The few other kilts were a mix of blues and greens, but there was one IOS with a lovely green tweed argyll.
I'm sure the dress code has adjusted to a more individual level, which to me is a good thing I think!