Chris, the blue Bavarian Litewka was replaced (by regulation) in March of 1916 by the Kleiner Rock. I'm sure, however, as this photo shows, that officer's with the former jackets did not pitch them. This guy is obviously in the homeland convalescing and has access to all of his uniforms.
I would think that the gray Schirmmütze would have been worn with the blue Litewka at least up until the time of the change to the Kleiner Rock and quite possibly beyond.