I swabbed Luke's cheeks a few weeks ago (which he wasn't a big fan of) and sent in the samples, and I finally got the results back!
It turns out that one of his parents was a purebred American Staffordshire Terrier, and the other was a Nova Scotia Duck Tolling Retriever Mix. I Googled that one to make sure it's real. (It is.) That's where he gets his color and almond shaped eyes.