I was at Pt. Pelee and the sun was setting over Lake Erie. The water was calm nearby, though there were waves further out from a wind from the East. The sun was very red and quite bright. The sky was clear and there were some typical bands of colour parallel to the horizon. I wasn't paying very much attention to the sunset because it wasn't exceptionally nice and the sun was bright.
When only a little bit of the top of the sun was visible, I decided to watch the sun until it disappeared. I was expecting it stay red and just disappear behind the horizon. However, as the remaining visible sun shrank to a point, it became whiter. It also seemed to get brighter, but I'm not certain about this. Then I remembered about green flashes. Right after becoming white, the sun started turning green. It reached a very pure green colour and it seemed quite bright. It gave me chills; I realized "This is it, I'm actually seeing a rare green flash!" After reaching pure green the spot shrank and faded and disappeared. It all happened very quickly, maybe within two seconds. It didn't feel too short though.
I'm so glad I saw that.