Tom,
your radiator should last a lot longer. What actually caused you to replace the orginal radiator? Flushing your radiator every couple of years will keep it flowing and pulling heat away from the engine effectively. Flushing will remove the acidic by-products of thermally decomposed glycol, mineral compounds, spent additives, and rust from the coolant system. Distilled water, or even "soft" water will help keep the coolant system cleaner and have less deposits. Maintaining a 50/50 to 70/30 mixture of antifreeze to water will provide freeze points of -35 to -67 degrees F (boiling points are 223 to 235 degrees F), respectively. As well as provide sufficient corrosion protection due to the additives added to antifreeze products. There isn't much I can add to what guzzi said above, everything he said was absolutely correct.

I believe you or someone was asking about a green color; I don't know if we are talking about outside the radiator, or on the inside. Many antifreeze products come with a yellow-green fluorscent dye for identification. Not all antifreeze is ethylene glycol, many antifreeze products are now propylene glycol. A green color is also indicative of copper rust compounds. If your radiator has copper coils, I guess over time a copper oxide patina/tarnish would form on the outside if not protected from evironmental conditions. My radiator fins still have black paint.

I've been thinking a lot about BigJim and his 100% EG filled coolant system. Granted, the boiling point for EG is way up there on the thermometer scale,something like 368 degrees F, plus what ever the 15 psi coolant system elevates the glycol's BP to. But the freeze protection would only be good down to about 8 degrees F. I don't see the advantage of having 100% glycol in the radiator; it's just what everyone else has been saying: The engine is seriously over-heating if the radiator coolant temperature is much over 220 degrees F. It's all about having a turbulent flow through the block to pull heat away from combustion chambers that are continuously firing at temperatures exceeding 4500 degrees F. Maintaining a clean coolant system with a 50/50 mix of antifreeze will pull sufficient amount of heat away from the block as long as the radiator is sized properly, and the water pump, thermostat, and radiator cap are all working properly. Guzzi's point about how a glycol-water mixture will pull heat away from the engine block more efficiently than a pure glycol liquid should be a definitive response to BigJim's Theory. No liquid commonly found here on Earth can tolerate absorbing as much heat as water does without flashing to vapor or thermally decomposing. But, pure water is corrosive to our coolant systems.

You know, there's one point I'd like to add, but it's probably not important in this discussion ... and that is that glycol is combustible and a toxic substance. Coolant leaks from BigJim's vehicles are much more of a concern than normally treated vehicle coolant systems.