glTF model exported from Blender is always black in Three.js

I am trying to import in my Three.js project a gltf model exported from Blender. The problem is that, in Three.js, all models materials are black (color: Color {r: 1, g: 1, b: 1}) while originally the mesh is green. I find this topic ( that show how to solve the problem in 3dsmax, how to solve for blender?
Here my code in Three.js:

var loader= new THREE.GLTFLoader();
  function(gltf) { scene.add(gltf.scene); },
  function (error) { console.error(error); }


Try to get the color of the material and put in 0xffffff or r:1 , g:1, b:1 and the model is going to be rendered with the texture. In Maya/3D Max you have to find difuse and put it in max value (0xffffff) I think

It has been solved by using Blender 2.8 and correcting normals and model materials, as detailed in this discussion: