The smarter and more knowledgable guys beat me to it, but I was going to say that my understanding is that there are so many Walker strands that there are several routes which one might choose in determining exactly which "clan" to claim.

I had a friend who was a Walker, and he decided to go with the tartan on Walker Shortbread boxes as the easiest route. It's a very ice red tartan, similar to MacGregor, I think.