Agreed, the red color of the Lowa Mountain Experts ($350) is indeed pretty cool! So of course you want to wear them and not plastics. Plus a leather boot is just more comfortable.
The Mountain Expert GTX
I really think theyll be fine. You can expect temperatures in the teens near the summit, maybe in single digits, and the insulated Experts should be up to that. To ensure you stay warm, be sure to use wool socks (SmartWool Expedition Trekking Socks; $20) over a good liner sock. You also can add insulated insolesInsolator Winter Insoles (available at Campmor) are $8, and add a layer of insulating Thermolite and neoprene beneath your feet.
Or, buy some vapor barrier socks (Integral Designs makes some for $30). These are thin, waterproof socks that you wear between the liner and oversock. By trapping moisture, they reduce evaporative cooling and leave your feet warmer. Take an extra pair of liner socks, though, as your socks will be wetter when wearing these.
Youll be wearing gaiters, of course. You could also take full overboots, such as Outdoor Researchs Brooks Rangers ($160). They cover the entire boot, and have removable insulating foam padding. But thats really for mountains such as Denali. On Orizaba, the few add-ons I mention above should be more than adequate.
Have a good trip!