My first recommendation is Concerning the Spiritual in Art by Wassily Kandinsky. First published in German in 1911, this seminal document calls for a spiritual revolution in painting that will let artists express their inner lives in abstract, non-representational terms.
This book is of interest to Labanistas because we know that Kandinsky and Laban moved in the same artistic circles in Munich (1910-1914). During this time, painters looked at music as a model for deeply expressive yet non-representational art. In this work, Kandinsky crystallizes the possibilities for an expressive visual art that consists of nothing but color and form. He also speculates on dance which abandons storytelling, writing “Both arts must learn from music that every harmony and every discord which springs from the inner spirit is beautiful.”
Did musical harmony and color harmony encourage Laban to look for movement harmonies? Take a flight with Kandinsky and feed your curiosity!