Pecos Hank has seen his share of storms, as evidenced by his cool footage of ominous green-hued clouds. He explains the science behind why massive thunderstorms can "go green," as they say in stormchaser parlance.
Some of the biggest thunderstorms can generate areas of concentrated heavy rain and hail that look like waterfalls. Storm chasers call this the core. Sometimes storm clouds part giving you a glimpse into the core aloft. If you're underneath the storm base, around midday, the core is often blueish or a gorgeous turquoise. But in the late afternoon and evening when most storm activity occurs, angled golden and reddish sunset light might mix with the blue precipitation core and the net effect is a greenish color. Yellow and blue makes green! Another way a storm can add a yellowish filter to the blue core is by kicking up a lot of dust. The more powerful the storm, the more wind, and often, the more dust flying through the air. Looking through this yellowish air into the blue core can also give a net greenish effect to a viewer.
Bonus video: his ten favorite tornadoes he captured: