How to paint imported landscape mesh based on color?

So I’ve imported the landscape terrain mesh from a different game that I want to prototype within UE4 (not using it commercially or anything). Anyway, in this game they have a terrain map you place on the landscape where green = grass, brown = dirt, etc.
I was wondering how I can achieve this using that terrain map?
Unfortunately it’s not possible to import all this stuff in the exported .obj with the game’s editor.

You will need some texture blending, like (in my video) here: UE4: Detailed Texture Blending with HeightLerp and Vertex Painting - YouTube
You can either use Vertex Color (a node of such name) or texture masks for it.

Regards,

Oskar