Left: SED fit (black line) to the WISE flux density measurements (blue points) of the GRG host (galaxy A), and the 2MASS extended source catalogue flux density measurements (green points). The WISE bands coloured blue (W1) and green (W2) depict the short wavelength bands which trace the evolved populations, and the bands coloured orange (W3) and red (W4) depict the long-wavelength bands which are sensitive to ISM heating of molecules and dust. In this way, early-type galaxies appear blue due to the dominant starlight component, while late-type galaxies and other actively star-forming galaxies will exhibit red colours. Right: WISE four-band view of the host system, with the colour assigned to each band as shown in the left of this figure. The GRG host galaxy is at the centre (A), with galaxies A and B moderately blended. While galaxies B–E have early-type colours, the host galaxy A has S0-type warm dust features.