Question: why are fruits and veg the colour they are?

Iain Moal answered on 23 Jun 2010:

This is because of the compounds they contain. The greens are generally due to chlorophyll. Reds, purples, blues and some other colours are often due to pigments called anthocyanins. Both of these are water soluble and can vary according to pH. Hence, these vetables can loose their colour when cooked too long in water. It is also the reason why blueberries in muffins made with baking soda (which is alkaline) can turn green.

The other main coloured compounds in fruit and veg are the carotenoids, which are named after the compound which makes carrots orange. Carotenoids aren’t water soluble, so that is why water cooked used for cooking carrots never turns orange.