  We present the rest-frame optical and infrared colours of a complete sample
of 1114 z<0.3 galaxies from the Spitzer Wide-area InfraRed Extragalactic Legacy
Survey (SWIRE) and the Sloan Digital Sky Survey (SDSS). We discuss the optical
and infrared colours of our sample and analyse in detail the contribution of
dusty star-forming galaxies and AGN to optically selected red sequence
galaxies.
  We propose that the optical (g-r) colour and infrared log(L_{24}/L_{3.6})
colour of galaxies in our sample are determined primarily by a bulge-to-disk
ratio. The (g-r) colour is found to be sensitive to the bulge-to-disk ratio for
disk-dominated galaxies, whereas the log(L_{24}/L_{3.6}) colour is more
sensitive for bulge-dominated systems.
  We identify ~18% (195 sources) of our sample as having red optical colours
and infrared excess. Typically, the infrared luminosities of these galaxies are
found to be at the high end of star-forming galaxies with blue optical colours.
Using emission line diagnostic diagrams, 78 are found to have an AGN
contribution, and 117 are identified as star-forming systems. The red (g-r)
colour of the star-forming galaxies could be explained by extinction. However,
their high optical luminosities cannot. We conclude that they have a
significant bulge component.
  The number densities of optically red star-forming galaxies are found to
correspond to ~13% of the total number density of our sample. In addition,
these systems contribute ~13% of the total optical luminosity density, and 28%
of the total infrared luminosity density of our SWIRE/SDSS sample. These
objects may reduce the need for "dry-mergers".
