comment: Colour is an interesting example, because we can see objects that reflect the same colours of light differently based on context. A classic example would be an optical illusion where two squares of the same colour appear to be different colours because on is contrasted with a lighter background.
  Out of curiosity, how do you resolve difference between two people's moral sense? 
  If for example two people disagree about whether two light are the same colour, we could compare the wavelenghts of light they emit and measure it objectivly.
  What's the equivilent for one person saying we should have the death penalty and one person saying we shouldn't?