This established the idea that Homeric Greeks had defective colour vision and that perhaps were colour blind en masse. It's been a hotly debated scholarly topic for over a hundred years. Bradley says that one of the problems with what Gladstone and subsequent scholars did was to attempt to map ancient Greek colour terms onto how we understand colour. That is, the idea of a spectrum of abstract colours that we've inherited from Newton, where we can close our eyes and picture yellow and orange and red and blue.