Why 2000 vw beetle cold light stays on and sometimes blinks?

When the cold light comes on it is because the Coolant/Antifreeze is still cold, and that you should drive moderately until the engine reaches normal operating temperatures. When it blinks blue it usually means that there is an electrical malfunction with the cooling system somewhere. (usually the coolant sensor goes bad) If the light blinks red then the car is overheating.