title: Why aren't these two nodes black in a red-black tree?
body: <p>As I understood it, in a red-black tree, when I insert a new node, and when I encounter a black node with 2 red children on my way down, I need to flip the colors, i.e. make the parent red and its 2 children black (except from the root).</p>
  
  <p>I saw this picture on Wikipedia:</p>
  
  <p><img src="https://i.stack.imgur.com/cC3mg.png" alt="enter image description here"></p>
  
  <p>Why aren't 8 and 17 black?</p>
  
  <p>I also check in a <a href="http://mainline.brynmawr.edu/Courses/cs206/spring2004/WorkshopApplets/Chap09/RBTree/RBTree.html" rel="nofollow noreferrer">applet</a> taken from "Data Structures and Algorithms in Java" by Lafore; same thing there, these nodes become black.</p>
  
  <p>Is there multiple of versions of this red-black tree?</p>