Colour-colour plot of the PCNTb catalogue at a common frequency 217 GHz. The red crosses show the 278 PCNTb sources inside the Planck GAL070 mask, while the blue pluses show the 1146 PCNTb sources outside the same mask. We can see the non-thermal and thermal source populations of the PCNTb; the non-thermal source population is dominant, as is expected from our selection criteria.