When X-ray binaries go into outburst, the optical and infrared (IR) emission tends to be dominated by the bright accretion disc.However, synchrotron emission from the relativistic jets can also be detected at optical/IR frequencies. I show that optical/IR colour-magnitude diagrams of the outbursts of X-ray binaries can successfully separate thermal disc emission from non-thermal jet emission, in both black hole and neutron star sources.  A heated single-temperature blackbody is able to reproduce the observed relations between colour and magnitude, except when excursions are made to a redder colour than expected, which is due to jet emission.  The general picture that is developed is then incorporated into the unified picture of disc-jet behaviour in black hole X-ray binaries.  At a given position of a source in the X-ray hardness-intensity diagram, the radio, IR and optical properties can be inferred.  Similarly, it is possible in some cases to predict the X-ray and radio luminosities and spectral states from optical/IR monitoring.