Good mud will enlighten you on how you can actually use muddy colors to your advantage. Now I'm not advocating you do this unintentionally. It's more about doing in purposely in order to use a specific technique. That's what you will learn in this lesson.
Note how I used the muddy block of color as a backdrop for the crayon & acrylics.
Try It - The best way to get familiar with this is to take some older, overpainted artwork and apply some acrylics, crayon, or whatever, to see if it connects with you.