A rainbow arc and the discipline of the stripe

A rainbow is the easiest thing in the world to paint badly: seven colours in a row, and they turn to mud wherever they touch. Whoever painted this one on a white plank wall kept it to six bands and let each one dry before the next went on, so every edge is clean.

The planks do the rest. Their grooves run straight down through every band, and against those hard vertical lines the curve looks rounder than it is, and the yellow brighter than yellow paint has any right to look.