What does it mean when the water warning light comes on in my 2004 Toyota Echo?

There are 2 lights , one blue, one red , they both will come on at starting , blue first then red , but that is to see if the are working , if you are driving normally and one of em comes on it means , Blue: Youre driving in very cold weather amd the coolant it getting below freezing point ,.( which is higly unlikely)

Or Red: your car is overheating

Can be a leak , defective water pump , thermostat , temp sensor