Colour-colour diagram of Herschel/SPIRE sources in the region of PHz G95.5−61.6. The coloured background indicates the average redshift in this colour-colour space for 10⁶ randomly generated synthetic SEDs (Amblard et al. 2011), modelled as modified blackbodies with dust spectral indices ranging from 1 to 2, and dust temperatures ranging from 10 K to 40 K. Sources detected above 2.5σ in all SPIRE bands are plotted as black stars. The five Herschel/SPIRE sources at 250 μm located around PHz G95.5−61.6, within the Planck beam, are indicated with red diamonds and labelled A, B, C, D, and E, as in Fig. 2.