Both green and red antifreeze are glycol based, but that's where the similarity ends. The composition of the additives used in the glycol is much different between the red and the green. The chemistry was changed for many reasons. The big reasons being toxicity and longevity.

The red antifreeze uses organic acid technology (frequently referred to as OAT) which causes metals to form a protective layer on themselves. It also uses phosphates, but no silicates. And it lasts a long time (5+ years).

Green antifreeze uses phosphates and silicates. It lasts 1-2 years.

Now, green antifreeze has worked well in engines for a long time, and I suspect that it would work well in a 4Runner as well. The problem is that you absolutely cannot mix the red and the green. This causes a nasty chemical soup that isn't going to do your engine any good. And flushing the red antifreeze, so that you can go back to the green antifreeze, is darn near impossible. Even if there is just a little bit left hiding somewhere in your cooling system, you will have a mess.