Coolant debate is like oil debate and everyone has their ideas of what to use and what not to use. I am far form the coolant expert but one thing I do know is you are not supposed to mix colors heavily. I've seen instances where certain additives will have a bad reaction with other additives and coagulate.
As for what we use: We use Prestone DexCool (orange) with a water wetter additive (1 bottle). Although I've heard GM techs say DexCool will corrode, clog, etc, we have not excperienced that at all. Likewise, I've heard to ONLY use Subaru coolant (blue), with mixed reasons as to why (head gaskets, radiator lifespan, etc) but have not experienced this as necessary...