You have an interesting topic.
I did a little research and I see that wax crayons served as vehicles for a teachable color theory in art education. See the following, from an article on the development of art media over the last two hundred years:
”...there was not a viable color theory which could be adapted to the public schools until Albert Munsell’s red-blue-yellow primary theory…. His color theory was manufactured through Prang watercolors, colored pencils, wax crayons, and poster tempera and distributed by the American Crayon Company.”
And later:
“The invention of wax crayons by Charles Bowlby in Danvers, Massachusetts, in the 1880’s also brought color in easily used form to the classroom.”
So you might consider looking at the crayon’s contributions to art education and to the progression of art generally. It seems interesting enough…
The crayon as an artistic medium though appears to have been neglected by serious artists, despite its importance. I guess it served/serves chiefly as a sketching tool. You could discuss that or look at some famous artists who did/do use crayons. The Impressionists and Picasso would be good examples for that. An article I found also suggests van Gogh used crayons early in his career because they were cheap.
I like your idea but it’s going to be difficult to find sources for it. I can upload the PDFs of these articles if you need them. There’s not a great deal in them but they may get you started.