→Basics of Gyms in Pokémon GO
In Pokémon GO, like the core series games, players can challenge Pokémon Gyms, which are shown on the map as large towers. If a tower is visible on your screen it can be selected from any distance away and its information can be scouted. The Gym screen will always show the Pokémon stationed there, the Pokémon’s CP, the Trainers who have claimed the Gym (if any), the Trainer’s level, and the battles won by the victorious Pokémon. Once the Pokémon is defeated it will be removed from the Gym and its stats will disappear.
If the tower is colorless, it means that the Gym is without an owner at the moment. You can give it a Pokémon so that you can gain control of the Gym immediately. Gyms automatically begin at level 2, allowing up to two Pokémon to be stationed there. A Pokémon placed in a Gym cannot be removed until it is defeated by a challenging Trainer, at which point the Pokémon will return to your collection so you can use it again. This Pokémon will return at
1hp, so remember to use healing items to restore your Pokemon’s health.
However, if the tower is colored red, yellow, or blue it means that one or more Trainers have claimed the location for their team. Trainers on the same team can use their team’s Gyms to train or fortify the Gym itself. Trainers on opposing teams will be prompted to challenge the Gym, potentially even to claim it in their team’s color.