I have seen them several times from the Northern Cascades in Washington. This was in summer and they were mostly green. Once from northern Minnesotta on the Ontario border in the Boundary Waters.
In Alaska and the Yukon I have seen them plenty of times. The best was up north of Fairbanks. By September the days are not as long. I got up to take a leak and the lights were in full display. I woke up a friend of mine. We got out the lawn chairs and had a couple of beers. We watched them for about 3 hours.
I asked some of the local people up there what they like to do in winter. They like to "build sweat lodges and have Northern Lights parties."