Named after the manufacturer of art materials founded in London in 1832, Winsor was the one who had a patch of white on his chest while Newton's coloration is all orange. Suspecting that no other Silver Spring business has a resident cat so visible to the public, I always enjoyed seeing either one lounging on the counter while a purchase was being made.
When I asked an employee if Newton, who was sleeping in the front window, was acting differently the response was that she seemed "happy!" Perhaps sibling rivalry extends to the animal kingdom as well.