Color Mixing-a solution for the vexed

It came up in class that a student had trouble with color mixing. As my students rotate and some come and go at different times I thought it would be easy and handy to have access to a guide like this for all students who were wrestling with this to have as a primer guide. I discovered this Magic Palette Artist's Color Mixing Guide and found it is available at
Magic Palette Artist’s Color Selector and Mixing Guide">Blick for $7.63 at 11 1/2" X 11 1/2" or 24" X 24" size is 20.80.