Hair Chalk Recipe and Application Tutorial

I have often have seen someone color their hair with bright colors.  But recently, I have seen women with streaks of variety of colors in their hair and have wondered how they do that.  While I am a follower of the Soap Queen, I saw this tutorial for a Hair Chalk Recipe and Application Instructions.  Thought this a really cool idea because I have never heard of hair chalk.  What is really great about hair chalk is that there is no commitment - it washes out in 2 - 3 shampoos.  Is this is too cool not to try. I bet it would be a hit.