article_snippet: For people with normal vision, the brain compares the signals from all three cones, enabling a person to see the colour of an object.
article_snippet: But for people who are colour blind, one or more cones will be missing or won't function normally, which means people who are colour blind will be unable to see the full spectrum of colours.
article_snippet: For people with normal vision, the brain compares the signals from all three cones, enabling a person to see the colour of an object.
article_snippet: But for people who are colour blind, one or more cones will be missing or won't function normally, which means people who are colour blind will be unable to see the full spectrum of colours.
highlights_snippet: One or more of the cones will be missing or won't function normally, meaning the person cannot see all colours .
  