I promised you a "winner" rating, and you got it, for the first image. The second one looks a little muted, but I'm thinking that's because the aurora wasn't as strong. In all images, you can clearly see the Big Dipper on the left, and Capella (Alpha Auriga) just above the horizon at center right. The reflections in the pond, silhouetting the trees along the back, really make this image.
The green is from oxygen atoms being pushed around in the lower atmosphere. Red comes from oxygen being stimulated higher up. Neutral nitrogen produces red/purple, and ionic nitrogen is blue. So the colours depend on how much radiation is penetrating into the atmosphere and stimulating the various atomic species.