This is a direct binding to the function “engine->LightStyle”. This function allows you to change the default light style of the map - so you can make lighting lighter or darker. You’ll need to call render.RedownloadAllLightmaps clientside to refresh the lightmaps to this new color.
Calling this function with arguments 0 and "a" will cause dynamic lights such as those produced by the Light tool to stop working.
Issue Tracker: #3626