why is the pH scale so similar to the rainbow?? which came first?? – Secondary 11

Question: why is the pH scale so similar to the rainbow?? which came first??
- Keywords:
  chemistry,
  colour,
  ph,
  rainbow,
  scale
Asked by cc2107 to David, Jonathan, Pete, Sam on 4 Jul 2012. This question was also asked by galkeviciute.
- Pete Etchells answered on 4 Jul 2012:
  
  That’s a good question! I think the pH scale is colour-coded to look like the rainbow because it’s an easy way of distinguishing between gradations of pH. Rainbows are a natural phenomenon, and we’ve known about them for much longer than the pH scale. So in that sense, the rainbow definitely came first!

Question: why is the pH scale so similar to the rainbow?? which came first??