Hi, in RUSTBORO CITY in PKMN Emerald there is a NPC which trades you a SEEDOT named DOTS if you trade a RALTS. So my question is "Can I shiny hunt that specific SEEDOT or not?".
Generation III saw an overhaul of many aspects of the game, which included the calculation to determine a Pokémon being Shiny. Shininess in these games is determined by a calculation involving the Original Trainer's ID number and secret ID number, as well as the Pokémon's personality value.
The Trainer who gives you DOTS (name KOBE) has a TID of 38726. As far as we can tell, DOTS has a semi fixed PID that prevents it from being Shiny, as do most Pokémon traded to the player by an NPC. :P
Source, 2, 3
Hope I helped!