If this coolant were to somehow leak out of the engine without the owners knowledge this could lead to the car overheating causing major engine damage. The level of damage caused by an engine overheating is very high and usually irreversible. An overheated engine will some and most times cause the engine parts to disorder themselves from the major heat being applied to them. The greatest example of these parts are the vowels, these allow the intake of air and gas.
With these overheated and disordered the car will NOT run. Getting an overheated engine replaced or fixed carries a VERY hefty price. So frequently check your cars coolant level, as it could mean whether or not if your car will ever be running again.