Kandinsky and abstract expressionists (and impressionists) were developing new ways to represent light. The technique was to free the painter from then traditional concepts of light and dark by combining black or white for instance, and instead they used values of color. To denote foreground from background, you could use lemon yellow juxtaposed with deep purple, etc. Careful study and composition based on hue, value and chroma is the basis of abstract expressionism. Also, the color represents the object and this was a revolutionary departure from representational art. This is very liberating for the painter but also needs a lot of thought, discipline and planning regarding composition, for an end result that looks spontaneous and effortless.
Note how in 'Holland Beach Chairs’ Kandinsky achieves a plein air quality to a painting that was meticulously planned according to his principles of color theory.
Kandinsky, 'Holland Beach Chairs'