A Lovat or Navy Blue coloured pair would work as well, although the Oatmeal-coloured also would work and would provide a nice contrast.

Lovat green or dark green would also work. The Lighter colours (Lovat) are usually more appropriate for day wear, whilst the darker colours are usually seen with formal or evening attire, although that's not set in stone, so to speak.

It is a nice tartan, and it's familiar to me, but I'm not quite getting it. It almost looks like the Campbell of Cawdor or Argyll District tartan...

Cheers,

Todd