FWIW, the answers to How much energy does displaying a webpage with a black background actually save?How much energy does displaying a webpage with a black background actually save? probably have the largest dissonance with regards to claimed values and community response. The top two answers (currently at +82/-2 and +59/-3) both contain no references and original research. The comments on both answers show a big split on opinion.
I don't have much to say in direct response, but this is a good case study of where the borders are.