Nope, the OW Sprites will be the regular coloration (even if it's shiny) until you catch it and put it as you first Pokemon.I know that shiny pokemon look shiny when they follow you. However, do pokemon with overworld sprites before you catch them (Lugia, Ho-Oh, Mewtwo, Suicune, etc.) look shiny before you catch them? It seems like that would make it much easier to SR, but I doubt it's what really happens.