Question: why are carrots orange

Tom Lister answered on 30 Jun 2012:

Good question. Carrots are orange because the absorb quite well other colours of light (red, yellow, green, blue etc.) but orange light bounces off them.

The particular pigment that causes this is called carotene (because it was first found in carrots). We also have carotene in our blood, although only a little bit, but it does make our skin look slightly more orange than it otherwise would (my skin at least, perhaps not somebody with dark skin). When I worked in radiotherapy, I once met a patient that was orange, because he ate too many carrots and he was sick, so his liver couldn’t get rid of the excess carotene.

Carotene is also what gives lobsters their colour, although it is coiled up into a different shape making them brown or blue (until you cook them – when the carotene unfurls and turns orange). This might be confusing, but most of the absorption of light occurs at the bonds between atoms, so if you change these, you change its colour.