My coolant is a dark color, what does this mean. I do not have oil or coolant leaking from my vehicle

What is your question?

The check coolant level message is on but when I looked at the coolant it is a blackish color not blue.

What makes this problem better or worse?

Running the engine at a stop light, the vehicle being idled while the engine is on

How long has your 2012 Mercedes-Benz E350 had this problem?

3 weeks but, I stop driving the car.