Or, it may be that the colored tunic is worn only by personnel while actively serving aboard a vessel.
Think about it. We saw a variety of uniforms in the first film, and the only place we saw people wearing the TOS-derived color-coded tunic was aboard the Enterprise itself. When we saw those same officers in other situations - Pike, Spock, Uhura, Scotty - they wore different uniforms or clothing. The same appears to be true in photographs from the second movie.