I'd go with black or red, or a "neutral" color like oatmeal.
WARNING!!!! Red will look great, BUT WILL be "look at me."

I tend to coordinate with the minor colors in the tartan for ones with a single main tone. One of the reasons I like my worsted Caledonia modern is that there is just enough going on that there is not a single main color, so all the tones look good as coordinators without any one being "too much."
As much as I LOVE school-bus yellow (am wearing a shirt in that tone RIGHT NOW), I'd avoid it with MacLeod "of Lewis" (wife's family has these roots)/Loud MacLeod. (Now with Wallace modern-or Gordon, or Macneil of Barra-, it LOOKS GREAT!!!)