  Photometric surveys at optical, ultraviolet, and infrared wavelengths provide
ever growing datasets as major surveys proceed. Colour-colour diagrams are
useful tools to identify classes of stars and to provide large samples.
Combining all photometric measurements of a star into a spectral energy
distribution will allow quantitative analyses to be carried out. We demonstrate
how to construct and exploit spectral energy distributions and colours for
sublumious B (sdB) stars. The aim is to identify cool companions to hot
subdwarfs and to determine atmospheric parameters of apparently single sdB
stars as well as composite spectrum sdB binaries. We analyse two sdB stars with
high-quality photometric data which serve as our benchmarks, the apparently
single sdB HD 205805 and the sdB + K5 binary PG 0749+658, briefly present
preliminary results for the sample of 142 sdB binaries with known orbits, and
discuss future prospects from ongoing all-sky optical space- (Gaia) and
ground-based (e.g. SkyMapper) as well as NIR surveys.
