The Canadair CL-415 is, IMO, a more practical solution than a huge plane like the Martin Mars. It can refill its tanks in 12 seconds and was designed for the fire fighting mission. It's very rugged and would be more maneuverable in tight places. Plus, the CL-415 would be a lot easier to maintain with modern (in production) turboprop engines.

I don't know if either plane would be all that useful in the Colorado or Arizona wildfires. Most Colorado lakes are pretty high above sea level, cutting into the plane's performance. Plus, both states are damned dry. Both of those planes would be better operated in places where a lot of water is handy.