Whilst green is not technically a formal colour, as Freelander says, if the jacket goes with your tartan, then go for it! I rather like the look of these jackets -- they would make one stand out in a crowd.

Tartanweb offers a green twill day jacket with Irish harp buttons & vest which is also very striking.

Scottish Lion was offering a blue charlie jacket --
A friend of mine who was ex-Royal Navy wore his mess dress jacket (in blue, of course) with his Anderson kilt, and it looked good -- but the Anderson has a lot of blue, so it matched.

Cheers!

T.