What you're describing is known as "Tagging for the Renderer" (see https://wiki.openstreetmap.org/wiki/Tagging_for_the_renderer).

OpenStreetMap would rather have correct data in its database than a single correct rendering of the map data. In this specific case, this object is a sports pitch for American football. It is not a water reservoir. Yes, the default map style on osm.org renders pitches with a green color, but if color is important to you, then the correct thing to do is to set up your own rendering pipeline and render the field using the desired color.