  The diverse behaviors displayed by X-ray binaries make it difficult to
determine the nature of the underlying compact objects. In particular,
identification of systems containing black holes is currently considered robust
only if a dynamical mass is obtained. We explore a model-independent means of
identifying the central bodies --- neutron stars or black holes --- of
accreting binary systems. We find four categories of object (classic black
holes, GRS1915-like black holes, pulsars, and non-pulsing neutron stars) occupy
distinct regions in a 3-dimensional colour-colour-intensity (CCI) diagram.
Assuming that this clustering effect is due to intrinsic properties of the
sources (such as mass accretion rate, binary separation, mass ratio, magnetic
field strength, etc.), we suggest possible physical effects that drive each
object to its specific location in the CCI phase space. We also suggest a
surface in this space which separates systems that produce jets from those
which do not, and demonstrate the use of CCI for identifying X-ray pulsars
where a period has not been established. This method can also be used to study
sub-clustering within a category and may prove useful for other classes of
objects, such as cataclysmic variables and active galactic nuclei.
