How to alter color of landscape during runtime?

Hello, I’m new to Ue4.
If possible, I would like to use code rather than blueprints.
I have a landscape which is the color green at the moment and I would like the landscape to vary in color randomly or in some loop.
The landscape uses a material to give it’s color, I looked on the api documentation and could not find any method or function to set or alter the material.
How can I do this?