Colours of Bulges and Discs within Galaxy Clusters and the Signature of
  Disc Fading on Infall
  The origins of the bulge and disc components of galaxies are of primary
importance to understanding galaxy formation. Here bulge-disc decomposition is
performed simultaneously in B- and R-bands for 922 bright galaxies in 8 nearby
(z < 0.06) clusters with deep redshift coverage using photometry from the NOAO
Fundamental Plane Survey. The total galaxy colours follow a universal
colour-magnitude relation (CMR). The discs of L_* galaxies are 0.24 magnitudes
bluer in $B-R$ than bulges. Bulges have a significant CMR slope while the CMR
slope of discs is flat. Thus the slope of the CMR of the total light is driven
primarily (60%) by the bulge-CMR, and to a lesser extent (40%) by the change in
the bulge-to-total ratio as a function of magnitude. The colours of the bulge
and disc components do not depend on the bulge-to-total ratio, for galaxies
with bulge-to-total ratios greater than 0.2. While the colours of the bulge
components do not depend significantly on environment, the median colours of
discs vary significantly, with discs in the cluster centre redder by 0.10
magnitudes than those at the virial radius. Thus while star formation in bulges
appears to be regulated primarily by mass-dependent, and hence presumably
internal, processes, that of discs is affected by the cluster environment.
