i have seen so many people having colored pokemon. can we catch them in wild? how did they get them? and what about pokemon which aren't found in wild? can someone please tell me? mention all possible ways to get colored pokemon.

Colored pokemon are promos and can only be traded\bought off other players,from the auction house and from the promo center as and when new ones are released

Shiny pokes can be caught in map. Also it can be bought in the promo center, from other people, Sabrina's shiny research or in auction house.
Colored pokes can be bought in the promo center, from other people and in auction house.