Transcript:

So, blueberries are blue because they contain this family of compounds called anthocyanins. Now, anthocyanins are unique. Here's what happens.

If you take blueberry and you make blueberry jam — now, jam contains only four ingredients: fruit, sugar, water, and lemon juice. When you make blueberry jam at home, you will find that it is pink in colour. This is because the anthocyanins, the colour that they exhibit depends on the pH of the solution that they are in.

All coloured fruits and flowers — not flowers — vegetables have anthocyanins in them. Take red cabbage, for example. Take red cabbage, boil it in water, save the water; it will be purple in colour. Now, add that water to vinegar, and it will change colour. Make a solution of detergent powder and add that water to the detergent powder; it will become a different colour.

You can generate a whole spectrum of colours in the kitchen just by playing with the pH of the solution. This is how it works. It's nature's version of litmus paper — anthocyanins.