Left: W1 − W2 colour vs. W2 − W3 colour of our 3326 target galaxies (black open triangles). The 303 sources above our IR colour cut are shown as red filled triangles. The two outliers with very red colours in the top right-hand corner of the diagram (magenta filled circles) are the low-metallicity and heavily obscured BCDs that were originally identified by Griffith et al. (2011). The two famous dwarf Seyfert 1 galaxies (NGC 4395 and POX 52), as well as a Seyfert 1 galaxy hosting a low-mass BH (UM 625; yellow filled circles), have WISE colours above our selection cut-off. Middle: same as left, but showing the AGN that have been previously identified in the MRBGD optical samples split into 549 type 1 (BL; green filled triangles) and 152 type 2 (NL; blue filled triangles). Although a large fraction of these optically identified AGN fall in our IR selected sample of 303 galaxies, many also have WISE colours below our selection cut-off (dashed line). The 43 candidate AGN, selected using the IR diagnostic, that are not in the samples of MRBGD are shown as red filled triangles. Right: same as left, but showing the 182 BCDs (cyan filled triangles) and the 2 low-metallicity and heavily obscured BCDs that were originally identified by Griffith et al. (2011; magenta filled circles). The BCD MRK 709 S (yellow filled circle), one of the most metal-poor BCDs with evidence of an active galactic nucleus (Reines et al. 2014), also has a WISE colour below our selection cut-off.