Incognito messiahs were painted oriental to mark them as not-yet-Christian

Evidence

In the story of the Marriage at Cana, Jesus and his disciples attend essentially incognito, hiding his identity as Messiah until the moment when he astonishes the crowd by turning water into wine. It was in keeping with an already established iconographic tradition that Veronese gave an oriental appearance to the participants who do not yet know Christ, but not to the party of Christ. — Ivan Davidson Kalmar, Derek Penslar, Orientalism and the Jews, 216