Question: Why are things certain colours? Why are oranges orange, the sky blue etc?

Joanne Sharpe answered on 12 Jun 2018:

This is to do with what structures of atoms make up the substance that your looking at. Visible light is a spectrum – when you see white light you are seeing all the colours in the spectrum. When you see black, all of the light is being absorbed by the object so you don’t see any colour. When you see a specific colour, it is because some colours are being absorbed and some are being reflected. The grass is green because chlorophyll (found in plant cells) absorbs all colours (wavelengths) except for green, which it reflects into your eye so you see only green. I hope this makes sense!