Infrared color-color diagrams for ExtEV. The position of ExtEV is marked by the cyan star in each panel. The blue dots and red triangles correspond to the B[e] SGs and LBVs located in the Magellanic Clouds, respectively. Their photometric properties were adopted from Kraus (2019). Black crosses refer to the sample of late-type SGs selected by González-Fernández et al. (2015). The shaded region in panel (c) shows the area with color index (K_s − W3)≳2 mag, where SGs with enhanced mass loss are suspected to be located.