Power supply flashes red and green, then reset button pops out

So either the gfi brick (power cord) has ceased being able to do it's job or (and this is equally likely/possible) it's doing it's job correctly and your actual power supply has developed a dead short. The version 1.0 xbox had a Foxcon power supply which had a design oversight/flaw. The solder joints on the power port could break and cause a dead short which in turn "could" cause a fire. So xbox release free of charge to all customers that GFI enable power cord. It's job is to trip and cut power if it detects a short in the power supply, this is to prevent a possible fire.

This is a potentially serious matter for which there isn't likely an "easy" fix. If you want you could try a different "known working" gfi power cord. If it still happens then the fault will definitely be the internal power supply. That would be the easiest place to start. I strongly advise against messing with the internals of either the gfi or the consoles power supply unless you know what you are doing/dealing with.