I too like to avoid mixing fluids or lubricants - even engine oil - if only for reasons of consistency and simplicity.

However, the attainment of VW approval (and not just a mere 'meets & exceeds' statement) by Penrite for their pink coolant is evidence enough for me that compatibility should not be an issue.

Having said all that, I normally flush the system after draining the coolant - even if I intend to use genuine coolant - so I guess it's a moot point for me anyway.