Light curves (left column) and instantaneous spectra (right column) obtained from the fiducial run in planar geometry (full lines) compared to the analytical expectations (dash-dotted lines). Normalizations of $\overline{T}$ and $\tilde{\nu }$ are defined at the RS. The top row display the result for a Band spectral shape, and in the bottom the synchrotron broken power-law. The respective contributions of each shock to the total observed flux (in black) are given in red for the RS and blue for the FS.