In this paper we investigate the correlations between spectral index, jet s
ide and extent of the radio lobes for a sample of nearby FRII radio galaxie
s. In an earlier paper we studied a sample of quasars and found that the hi
gh surface brightness regions had flatter spectra on the jet side (explicab
le as a result of Doppler beaming) whilst the extended regions had spectral
asymmetries dependent on lobe length. Unified schemes predict that asymmet
ries resulting from beaming will be much smaller in narrow-line radio galax
ies than in quasars, and we therefore chose to investigate, in a similar fa
shion, a sample of radio galaxies with detected jets. We find that spectral
asymmetries in these objects are uncorrelated with jet sidedness at all br
ightness levels, but depend on relative lobe volume. Our results are not in
conflict with unified schemes, but suggest that the differences between th
e two samples are primarily due to power or redshift, rather than to orient
ation. We also show directly that hotspot spectra steepen as a function of
radio power or redshift. Whilst a shift in observed frequency owing to the
redshift may account for some of the steepening, it cannot account for all
of it, and a dependence on radio power is required.