I started all over On Firered then all the way to Seafoam Islands. I was next to an Articuno and save. I guessed it was different and I pressed A on the Control Pad and Wild Articuno appeared with Light Blue colored Articuno.
You are so lucky, unfortunately, I killed the only shiny that I foun since I started playing Pokémon more than a year ago (it was a mankey), but I don't like the shiny legendaries.