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.
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.