Blue coolant
 

I've just noticed that the coolant in my B5,5 with PD 130 is a clear light blue colour. I know it's meant to be pink G12 but obviously someone has replaced it with something else.

Is this likely to cause a problem? I'm guessing if they hadn't flushed the system first then it wouldn't be so clear. Should I look at flushing the system out and sticking G12 back in?

How difficult is a flush on these?