I still like Oatmeal for formal and colours for more casual. The oatmeal will really show off your flashes, not hide them on a colour background.
Lot's of options to choose from and most of them are usally wearable with more than one kilt. I only have a few colours that I interchange with the kilt i'm wearing and the occation i'm attending.
Oatmeal dosn't stand up in the dust or rain soaked mud of a weekend festival. Black, olive green and blue hide the dirt and beer spillage of a good night at the concert beertent.

Kilted Stuart