Only ever open a cooling system when the engine is cold. A hot system is pressurized and will spray scalding coolant the moment the cap turns.
Check the translucent overflow reservoir, not the radiator cap. There are MIN and MAX lines on the side and the level should sit between them when cold.
Coolant color is not decoration — it indicates chemistry. Mixing types can gel the system. If you are topping up more than once a season, you have a leak worth finding.
