The Moonbow is, as the name suggests, caused by the moon. It is less bright than a regular rainbow and it appears to be white to the human eye even though it’s capable of capturing the colors of a long-exposure photo.
The Moonbow can be seen in places near waterfalls or when there are rains in certain conditions: the full moon shouldn’t be too high in the sky and the sky itself should be dark. The size of the Moonbow is pretty much the same as a regular rainbow.