The design is obviously still printed at a much reduced scale, so we wouldn't need such a big area to see different colours.
You may remember me saying that I am not painting the mural directly onto the wall, but that it will be printed onto special, heavy-duty 'wallpaper'. There were 4 possible textures to choose from, so the printer took the left hand end of the artwork and printed it onto each of the papers. One is totally smooth, the other three have different surfaces:
For some reason, the smooth paper makes the colours far sharper and brighter, so that was the obvious best choice. There was a nervous moment, when the library management had to do costings and find out if the smooth paper was much more expensive, but it turned out to be the same price (phew), so that's what we are going for.