I like to throw in a little friendly "challenge". Marvin has a three
Student Gallery pages on his web site. For anyone doubting the effectiveness of this approach, I would google the students and look at work done prior to the workshops and after the workshops.
The results speak for themselves and that for me is all the validation necessary to prove that this technique can make a change in the way students learn to deal with color. As Marvin said, this method has been around for years. He just happens to be one of the very few instructors who I have found, who teach this method.
Just as Allan pointed out there are many ways to reach similar results, but why struggle for years, when there is an easier way to learn?!