Why does the moon turn red sometimes?

This is a simple answer really:

The moon doesn't actually turn red. It's all about the way light reflects off the moon and hits your eyes. Colours are bent when traveling through the atmosphere and sometimes the moon appears red because the colour red is absorbed by your eyes. Usually, when something like this happens it is when the sun is setting and you can vividly see all of the colours that your eyes reflect.

The moon turns red sometimes because the moon lines up with the Earth and the Sun. This is called Lunar Eclipse.