After 50+ years of kilt wearing, my 'flashing' seems to follow a pattern - not rules.

Basically, tartan flashes are a fairly modern innovation and have crept into the scene over the past twenty years or so - as really has the wide range of plain coloured flashes now available. Back in the 1950's, the only flashes one could find were either red or green - that was it!

I generally wear Tartan flashes when dressing formally (and occasionally, when I do not have suitable plain ones).

Plain coloured flashes are best matched with the base-colour of the kilt and, yes, if plain flashes and plain tie match, you will look really good.

When dressing casually, with my kilt hose worn normally (ie: pulled up) I seldom wear flashes - just elastic garters under the fold over tops. If I do, then they will be of a plain colour, perhaps to tone with my shirt or top rather than the kilt. Of course, flashes are totally unnecessary and pointless if the hose is rolled down!

I hope this helps.