In nature, blue is much rarer than you might think. Sure, the sky is blue when the weather's nice, and so is the ocean. But the vast majority of plants and animals are incapable of making blue pigment. Brilliantly-coloured peacocks appear blue not because their feathers are coloured that way, but because of how they reflect light. Less than 10 per cent of the world's 280,000 flowering plants produce blue flowers, which may be why they're often a symbol of the unattainable in folklore and literature.