Most radiators now are aluminium and this has given rise to different schools of thought.
The color doesn't mean a thing anymore. What is inside makes the difference.
Traditional ethylene glycol
Uses silicates to passivate metal surfaces to prevent corrosion. OK to use in European based designed cars (Daewoo and Daewoo engineered Chevies as well). Cannot be used in Japanese cars.
Ethylene glycol - no silicates
Used in Japanese cars. Due to the seal materials used in their designs, the silicates will precipitate out and become abrasive stuff. Uses phosphates to inhibit corrosion.
Ethylene glycol - low silicates, low phosphates
Used in the new European cars. They got a problem with phosphates foaming from Europe's hard water (as if distilled water can't be found in Europe
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).
Monopropylene glycol
Does not conduct heat as well as ethylene glycol but is reported less toxic. Carries no recommendation from any car manufacturer. Some caution against using it.
Organic acid technology
OAT as they call it. AKA GM-Dexcool (or Deathcool to some
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) Recyclable and biodegradable antifreeze which is based on organic acids and is silicate- and phosphate-free. Due to the nature of the chemicals used, it can attack certain seal and gasket materials and therefore should only be used in vehicles for which it is factory specified.
DO NOT MIX glycol based antifreeze with OAT ones! If you must, you have to chemically flush your coolant system before changing over!
Ethylene Glycol-based Hybrid Organic Acid Technology
They call this HOAT. Prestone's yellow/orange 5/150 is HOAT based. It uses glycol and OAT based corrosion inhibitors. There is some silicate added. Most of them uses BASF's "Glysantin" additive. Less agressive than straight OAT and offers better cavitation resistance. Like OAT, best to flush your system thoroughly before using. Another nice HOAT based antifreeze is Valvoline's Zerex G-05.