a) m(3.4 μm)–m(4.6 μm) vs. m(4.6 μm)–m(12 μm) colour–colour diagram for a sample of emission-line galaxies detected in the three WISE bands 3.4 μm (W1), 4.6 μm (W2), and 12 μm (W3). Galaxies with equivalent widths of the Hβ emission line EW(Hβ) ≥ 50Å and L(Hβ) ≥ 3 × 10⁴⁰ erg s^-1 are shown by filled red circles; galaxies with EW(Hβ) < 50Å and L(Hβ) < 3 × 10⁴⁰ erg s^-1 are depicted by open blue circles. The galaxy with m(3.4 μm)–m(4.6 μm) = 2.73 mag (J1353+1649) discovered here, is shown by a large black filled circle in all three panels. b) W1–W2 colour vs. oxygen abundance. The sample is split into two parts with high and low EW(Hβ). Nearby galaxies with redshifts less than 0.01 are presented by crosses (red for the galaxies with high EW(Hβ) and blue for low equivalent widths of Hβ). The remaining galaxies are presented by the same symbols as in a). c) W1–W2 vs. EW(Hβ) is shown for nearby galaxies (redshift z< 0.01, black crosses) and for more distant galaxies (z ≥ 0.01, filled magenta circles).