WISE colour−magnitude and colour−colour diagrams for classification of sources, showing the colour−magnitude and colour−colour criteria (black lines), AGN-classified sources (grey points with black edges), PAH/star forming galaxy-classified sources (white), shock-classified sources (yellow), resolved PAH emission-classified sources (purple), Class I-classified sources (red), Class II-classified sources (orange), and unclassified sources (small grey points without edges).