Why do the eyes of this cat have different colours when viewed from different angles?

Why do the eyes of this cat have different colours when viewed from different angles?

Both of the eyes of this cat appear yellow when looking straight at the camera.

However, when the cat looks at an angle to the camera one eye appears green. Unfortunately, the cat is not mine and I don’t have many more pictures of it.

I have also noticed that my own eye which appears dark brown from straight on, looks lighter when viewed from an angle.

Why does this happen? Is there a special property of the iris that lends itself to such behaviour? In this website, it is mentioned that the colour of the iris varies with the angle at which it is viewed but no explanation is given.