Lines represent the 500mb height field, which is used to determine location and orientation of troughs and ridges. Additionally, assuming coriolis and friction forces didn't exist winds would flow parallel to height lines, which isn't a horrible assumption 99% of the time.
Colors indicate vorticity, which indicates the tendency for atmospheric rotation. This graphic only depicts positive vorticity (i.e. cyclonic rotation). Pairing cyclonic vorticity with wind yields cyclonic vorticity advec