The sun low on the horizon often provides the most colorful light of the day. It had rained and above the clouds were just thinning, and the sun dropped under for a few minutes.

Denis McCabe and I went down the west bank of the Rhein in Köln, and I made this view of a tram crossing with a fleeting rainbow in the eastern sky.

Yes, there’s a bit of luck involved, but also it helps to recognize when the light is about to get interesting.