Beauty is more than skin deep. In nature, colour is more than a source of beauty; it's a form of vital communication. Depending on the situation, colour says different things - it can be an expression of power or seduction, warning or deceit - and it can even, occasionally, save your life. Accompanying a major new BBC series with David Attenborough, 'Life in Colour' explores the fascinating story of how colour works in the natural world.