The side skirts cover most of the tracks of the Merkava. For this reason I found convenient painting the running gear before assembling the rest of the hull.
I painted the wall and the suspensions with an heterogeneous coat of dark brown. Moreover, in order to provide a base for further weatherings, I darkened the shadows with black. Note however that very little of it will be visible, after completing the assembling.
I airbrushed the wheels, the return rollers and the sprockets with the acrylic paint Vallejo 70.991 Dark Sea Grey, then I faded them in the center with the same color lightened with Vallejo 70.976 Buff. After that, I painted the rubber edges of the wheels with a fine paintbrush, using a mix of black and Dark Sea Grey, and I colored the steel edges of the return rollers with Model Master 1780 Steel enamel.
Finally, I airbrushed the tracks with a very dark brown.
This is how the fully assembled running gear looks like, with and without the upper hull.