Changing the default color of x, y, z in MeshNormalMaterial

I know this question has already been asked on Stackoverflow here: but could someone provide an example of how this can be done? I cannot see in this example how the color was changed.
What do I need to do to override the x, y, and z colors with my own custom colors?

Some code:

var box_geometry = new THREE.BoxGeometry(1, 1, 1);

var material = new THREE.MeshNormalMaterial({}); // what do I have to change here

var cube = new THREE.Mesh(box_geometry, material);

It doesn’t have to be a full answer, just a few tips would be really helpful.

Found this answer: Changing Normal Material Color. I guess it’s fine then.