In this first episode of Series 5, Stephen talks to David Hockney and uses Homer's verse and a bilingual Italian to show how the way we match words with colours reveals how language works. Colour is subjective and emotive. The phrase 'colourful language' is a metaphor for vividness. But until recently, we've been confused about how colour language developed. William Gladstone a Homer expert - helped show that most ancient cultures had no word for blue, so it was concluded that the ancients had under-developed colour vision. The reality was that they had under-developed vocabularies. We meet a man who sees no colour but hears it electronically and can ''name'' colours with audio signals. We also hear from the head of colour marketing at Dulux whose job it is to find new words for new colours. And a bilingual woman says she might think differently about colour depending on which language she's using.