Here is an article
that talks about Lazuring classroom walls, it mentions
"In a Waldorf environment, colors for classrooms are chosen based on the age and developmental stages of the children. For example, a kindergarten classroom will feature rose and magenta tones, while an upper grade classroom (7-8) will have walls of aqua, green and blue."
I think Steiner also chose the colors based on the specific school--in addition to developmental stage.
Most kindergartens I've seen are pink, and in our W. school now it's---grade 1 peachy, grade 2 more orange, grade 3 yellow, grade 4 teal, grade 5 light blue, grade 6 darker blue, grade 7 blue/violet, grade 8 violet