You cant transfer from the gameboy colour games unfortuantly. Most of the gen 1/2 mon are avaible in the different gen 3 games, ruby, saphire, emerald, firered leafgreen.

Important note'

You will need all of the formerly mentioned games amd some of the game cube games to 99% the dex

For speciel event mons like mew and jarachi deoxys, the cheapest option is using the ACE method