The eye is the portrait variable
Border Collies hold direct eye contact at a level no other breed does. The portrait has to preserve that intensity rather than softening it toward a friendlier register. We read the focused expression from your photo — the slightly lowered head, the locked gaze, the alert posture — and holds it. Knight and Meadow especially flatter the working stare without sentimentalizing it.
Black-and-white or red-and-white
Classic Border Collies carry black-and-white markings with a white blaze, white chest, and often white legs. Red-and-white variants substitute liver-red for black. The markings are individual — symmetric blazes, asymmetric face patches, full collar or partial. Each rendered as your dog has them rather than normalized. Watercolor handles the soft edges where black meets white especially well.
Where the breed lands hardest
Meadow, Highland, Mountaintop, and Watercolor are the natural fits — outdoor formats that honor the working herding heritage. The breed reads in landscape better than in interior scenes because that's where it actually lives. Knight works for portraits that want to formalize the dog. Pop Art can flatten the markings into shapes; the breed's specific patches lose definition.