title: UNITY-Changing ONLY certain part of 3D model's color
body: <p>I'm really new with unity3D and I would like to ask a question
  I have a 3D human model ( a default unity model) which has a hierarchical bone structure.</p>
  
  <p>What I want to achieve here is, when I press certain trigger, I want to color one of its limb with different color (just one of its limb). This is the illustration of what I want to achieve</p>
  
  <p><img src="https://i.stack.imgur.com/0KFnk.jpg" alt="enter image description here"></p>
  
  <p>I'm really clueless about this, because I've just started learning Unity for about 3 months ago, so I really need your help, this is the property of my renderer if it's helping</p>
  
  <p><img src="https://i.stack.imgur.com/GUebC.png" alt="enter image description here"></p>