I saw the Wolf Kahn idea from another blog, I don't have my plans at home but will credit you as soon as I get there! I changed a bit and did a resist with the oil pastels and watercolors. Day 1 we looked at art by Wolf Kahn, discussed a resist, blending and analogous color schemes. Day 2 the students choose 3 analogous colors from the wheel and we used a wet-on-wet watercolor technique to get blending results. These are two student examples and they turned out pretty good. Any oil pastel color could have been used, just making sure it wasn't part of their analogous color scheme.
PS-Just found where I got the original idea: http://onecrayolashort.blogspot.com/search/label/Artist%3A%20Wolf%20Kahn
which I notice is way different than they way I did it. That's why I love the art blogs because we each see an idea and make it in our own way!