You often hear stories about storm clouds turning green before a tornado touches down.
The explanation is the same type of thunderstorms responsible for the majority of violent tornadoes also may produce copious amounts of hail. These thick hail downdrafts or hail cores often have a blueish turquoise glow. Makes sense doesn’t it that an icy waterfall would be blue? These mega storms or supercells also occur mostly in the late afternoon and early evening when scattered yellowish sunlight blasts into the hail core… and so the yellow and blue make green. More often than not, these greenish supercell bases do not produce tornadoes so to associate green clouds as heralding a tornado is incorrect. In my experiences, these tornado producing storms also may have a green hue because they are ingesting copious amounts of dust. This dust often has a yellowish or brownish filter affect on the storm and thus blending with the blues and grays and giving the storm an eerie green hue.