In Pokémon GO, the color of a PokéStop can indicate its current status. If a PokéStop is yellow in the details, it generally means that it is a “controlled” PokéStop in the context of a team, with that color representing Team Instinct. This color coding is part of the game’s mechanics related to gym battles and the faction system, where different colors represent the three teams: Team Mystic (blue), Team Valor (red), and Team Instinct (yellow).
Keep in mind that the visual indicators for PokéStops can change with updates or events in the game, so it’s always a good idea to check for the most recent information directly from Pokémon GO resources or community forums.