(Chemistry professor Joe Schwarcz): Thanks to chemical ingenuity, we lead a colourful life. Synthetic dyes have served up a feast for the eyes but they may leave us starving for good health.
Our reliance on these chemicals exposes us to a host of unnatural wavelengths that can affect our body chemistry. Until about 150 years ago, we had no choice but to rely on natural dyes. If you wanted red, you had better know where to find a madder plant. Blue came from indigo, purple from a type of mollusk.