I've seen lots of versions of this project on various blogs and Pinterest, and here is my take! The concept worked great for my third graders at Suffield because I focused on color theory for my SLO with them this year. This was our culminating project where the students used the info we'd already learned about color families to create the artworks.
They did the majority of the color work with watercolor crayons. This worked great for mixing the secondaries. They used metallic gel sticks (School Specialty's version of Slick Stix) around their tint/shade frames and they worked really well.