Can somebody explain this image? If you had raindrops in only those four positions, this might make sense, but I think there are more than four static drops and thus angles.

Edit: staring at it helped. Anything that hits your eyes in a certain way comes from above a certain angle and has to have traveled and been refracted in a certain way, anything below a different angle is the opposite. Hence the opposite order to the rainbows and the difference in intensity from the difference in length of the path (which loses more light on each change in direction).

Not exactly correct, but close enough for my brain to stop trying to figure out.