cindy,

I found this on the Weather Corner

http://ggweather.com/wx_corner.html

"Q. During our recent spectacular lightning show I noticed that sometimes there was a greenish tint to the lightning. Can you explain this? Lucy Baldwin - Palo Alto

A. Clouds often take on a greenish hue before severe storms, but this is most often associated with hail. Hail is usually part of a thunderstorm. These tall, dense cumulonimbus clouds often block most of the sunlight, so the greenish tint may be a reflection of Earth's green foliage. However, the cause of the green tint has not been proven conclusively."

or it might be power lines...

gonyen