assuming you mean without a gameshark cheat code, the only way to get a shiny Pokemon is just luck, i think its one in every 3600 wild Pokemon you encounter or something like that, but i found one at...
Search every where there is Pokemon and eventualy you will get one. (Note: in Pokemon silver if two Pokemon you put in day care had an egg it had a 50% chance of being shiny.)
you might be referring to a "shiny" Pokemon it is a Pokemon with a different color then its average species example is a gyrados: mainly there blue but a shiny gyrados is red its as close as an...