Alireza Khajehali has shared a colorizer function for Unreal Engine 4 users.
From large surfaces such as landscapes to smaller objects like rock formations. World space color variation is always the key to make things look more natural and interesting. This function gets your Albedo and outputs parameters to the material instance for you to introduce any sort of color variation to the surface at any scale, using a single RGB Texture Map.
You can download the function from here.