+1 on not belieling that peple still run their cars on just water.
I've used any random cheap antifreeze I could fing on all of my cars i.e. BMW, Skyline, WV etc. Everything worked perfect and didn't overheated once. In fact, on my R32 I still use my shit n/a rad with welded holes (lol) and broken bits, and it never overheated, even when temperature was more than +30*C on a drift day. Reasonable driving with lots of cooling laps etc helps like hell.
I was told at my old job that you can mix green, blue and similair colours, but never red and yellow. In uni we were told that you cannot mix anything. I did added a little bit of green A/F to girlfiends Polo with red A/F to stop overheating due to extreme low level of coolant, nothing bad happened, nothing's clogged etc, but that's because it's a very basic engine.
Personally I use green A/F because almost all of my cars had green A/F before me.