Blue Thermostat light sensor on 1998 Volkswagen Beetle

My thermometer light turned from red to blue and car quit in driveway and will not start back. This is the diesel car.

Any suggestion? Will turn over but not start.

Asked by for the 1998 Volkswagen Beetle
Really need to Check the Engine Computer for codes. The Blue light means that the Engine is cold and so the Diesel Engine Turbo Charger is held back until the Engine Heats up completely. The Red light means there is a fault condition.