The majority of the OEM brake system for the car (calipers, pads, rotors, hydraulics, fluids) are manufactured by a company in Germany named "ATE". This company supplies the brake components to MB / Karmann to assemble into the car. ATE manufactures multi-level grades of brake fluids from OEM to Racing and each of these grades of brake fluids are provided in both yellow and blue. The reason they provide the same spec. brake fluids in two very different colors is so when you are flushing your entire hydraulic braking system, you will know when the old fluid has been removed and the new fluid has taken it's place.

In very simple terms, you could hypothetically get a Crossfire with yellow ATE brake fluid in the system from the factory. Then when you need to flush the entire hydraulic system and replace it with fresh fluid, you would use the ATE blue fluid so you know (visually) when the old stuff has been completely removed from the system when the old yellow fluid has been pushed out and now is completely blue. And vice versa.

So don't worry if you got the same product # of ATE brake fluid, being either yellow or blue. It just goes to show you that the mechanic is not smart enough to follow the procedure and has now turned your brake fluid to green.

Just follow this procedure. if you have yellow fluid, then when necessary to flush the entire system, use blue fluid and then when necessary to flush the system again, use the yellow... That way you will always know when the new fluid is purging through the bleeders at each wheel and replacing the old stuff in all the hydraulic lines.

Sorry, I just realized your were discussing coolant fluid... The same technical specs. apply to both systems.