I would describe your pretty boy as a blue point domestic shorthair. He's lovely!
Most cats are not any particular breed. The colorpoint gene (responsible for his pointed coloring) originally came from the Siamese breed many generations ago, beginning in the 1950s-60s when that breed became popular. At this time, the colorpoint gene is widespread in the domestic cat gene pool and doesn't indicate recent Siamese ancestry; pointed cats are common in the domestic cat population (but that doesn't make them any less special and beautiful ).