How convert color codes generated from threejs THREE.MeshPhongMaterial to HEX

Question

When used like thisin threejs

const INITIAL_BODY_MTL = new THREE.MeshPhongMaterial({ color: 0x374047, shininess: 10 });

It is creating a object with changing color codes

 {
  "color": {
    "r": 0.21568627450980393,
    "g": 0.25098039215686274,
    "b": 0.2784313725490196
  },

How to change that to normal HEX. As I searched and found those are float64 format But I am unable to convert to HEX using Javascript