Follow, follow, follow, follow, follow the...green brick road. It doesn't work, does it? It doesn't even fit the song properly. And yet that's nearly what we ended up with on screen.
When we say Technicolor was a really new technology at the time, we mean it. They were still working on calibrating the cameras to pick up and correctly display colors properly on film reels. To the horror of the producers, when they shot their first scenes on the yellow brick road and rolled the tape back to look at them, the yellow coloring was showing up as a vivid green. The set had to be completely repainted several times as they experimented with different shades, before finally finding a solution that would give the desired effect. The yellow brick road Dorothy and her friends finally walked down to the Emerald City was probably six inches thick with it by the time they were done.