A bright green light, like a giant traffic light, lit up for 2 seconds, twice in 20 second illuminating five miles of mountain range.My wife and I were driving North from Kona towards Waimea. We were at close to Waikaloa when we saw the light. A bright green light, like a giant traffic light, lit up for 2 seconds, and illuminated the mountain for probably five miles. It then happened again 20 seconds later, but not again after that. We were sober. I am in construction and am very familiar with commercial and industrial tools and equipment, and I cant imagine anything making that much light, that color, besides an electrical transformer exploding. But the was not an explosion. There were no signs of smoke, air craft, trails, just the light flashes. We were probably 40-50 miles from the mountain range on a night with good visibility. Every car on the road in front of us must have seen it too. It is also worth mentioning that the area on top of the mountain, doesn't have any military activity and is mostly pasture land, with no industry, that I know of.