Here I will go over how to get RGB textures working in Blender. First we need to delete the image that was first used. There is 3 of them.

Once they are removed drag in the new ones to replace them. There 3 main files RGB, Normal, Metallic. Once you understand these maskings youll be able to apply more. For now lets just do RGB.

Now plug in the Nodes as they were originally. You should then see the texture change that the mesh is applied to. For this I will plug in the same file but here is where you can add different effects to meshes with Normal and Metallic texture.

These color wheels are ways to change the RGB channels. As you can see here I have modified this texture to be different colors just by using the wheels. Black and White are used for Alpha on some wheels changing them will let colors fade into others. 

Comparing the original to the modified one you can see all channels have been changed in some way.

It could take awhile to dial in the correct colors but once you get it it becomes very simple on whats happening. When ready click on this icon and go down to bake. Be sure to have the node selected!

Youll see a little progress bar at the bottom. After it completes you should now see an override to the texture channel. 

Final step is to save the file. Go up to 3bars icon > Image > Save As. Now youll be able to save baked file to your computer.