  We present a study of pixel Colour Magnitude Diagrams (pCMDs) for a sample of
69 nearby galaxies chosen to span a wide range of Hubble types. Our goal is to
determine how useful a pixel approach is for studying galaxies according to
their stellar light distributions and content. The galaxy images were analysed
on a pixel-by-pixel basis to reveal the structure of the individual pCMDs. We
find that the average surface brightness (or projected mass density) in each
pixel varies according to galaxy type. Early-type galaxies exihibit a clear
``prime sequence'' and some pCMDs of face-on spirals reveal ``inverse-L''
structures. We find that the colour dispersion at a given magnitude is found to
be approximately constant in early-type galaxies but this quantity varies in
the mid and late-types. We investigate individual galaxies and find that the
pCMDs can be used to pick out morphological features. We discuss the discovery
of ``Red Hooks'' in the pCMDs of six early-type galaxies and two spirals and
postulate their origins. We develop quantitative methods to characterise the
pCMDs, including measures of the blue-to-red light ratio and colour
distributions of each galaxy and we organise these by morphological type. We
compare the colours of the pixels in each galaxy with the stellar population
models of Bruzual & Charlot (2003) to calculate star formation histories for
each galaxy type and compare these to the stellar mass within each pixel. Maps
of pixel stellar mass and mass-to-light ratio are compared to galaxy images. We
apply the pCMD technique to three galaxies in the Hubble Ultra Deep Field to
test the usefulness of the analysis at high redshift. We propose that these
results can be used as part of a new system of automated classification of
galaxies that can be applied at high redshift.
