posted on Jul, 11 2013 @ 09:49 PM
What you describe is consistent with inter- (or intra-) cloud lightning, probably quite high up in the atmosphere. You probably wouldn't have heard
any thunder because it's so far away. Lightning like this can appear very eerie, with strange colours and strobe-like effects.
I remember an event on a summer night in the English Midlands about 20 years ago, when hundreds of people called the police, airports and the military
reporting strange lights in the sky. Many people thought they were seeing UFOs, but they were actually witnessing a high-level electrical disturbance
in the atmosphere about 120 miles away on the ground and five or six miles in the air.
Then again, your sighting may be nothing of the kind - it's fascinating whatever it is.