How to alternate images in 2d unity

Hi,

I am trying to change the images of sprites in a scene. I have Background, Player, and Enemy and i am trying to have them change colors throughout the game. There are four colors total and I just need to have all the scripts in the scene change into those four colors at random times throughout the entire game never stopping. So when the game starts have them all one color and then change between those four colors at random times. They don't have to change at the same time but just change whenever. If anyone knows a way to make this happen or what script i need to use please let me know!

Thank you!