My 2007 E92 325i has 'for life' coolant and routine flush and replacement is (allegedly) not required. Ignoring the wisdom of that can someone tell me what colour the 'for life' coolant should be?

What is in there at the moment is definitely green.

I want to get a litre bottle to 'top-up' should it be necessary but if what is in there is non-standard I'll have to do a full drain and refill.

If someone knows the answer to this I will be grateful.