I am a Macdonald of Keppoch and I don't even own a Macdonald of any sort kilt yet.

I have a Black Watch (considered universal)
Gordon (another regimental tartan)
and a new Irish County tartan which my Mom and sister picked out as a pretty pattern. (we are in the process of making matching skirts and arisaids for the girls to match my kilt.)

I do have some of my clan's tartan which I hope to make a box pleat of, but unless there are legal restrictions placed on the tartan (there won't be any to stop you if you order a stock tartan.) you can wear anything you like.

Now if you're more comfortable wearing colours that are related to you somewhat. Go for it.