Left panel: ABC sources with a WISE counterpart detected in all four WISE bands (white circles) represented in the w1 − w2 versus w2 − w3 color–color plane. KDE isodensity contours containing 90% of the Roma-BZCAT sources detected in γ-rays (as reported in 4FGL catalog) are presented with lines of different colors for the different Roma-BZCAT subclasses, as indicated in the legend. Filled circles of the respective colors mark the γ-ray blazar candidates of the different subclasses (see main text). The ellipse indicates the average color uncertainties. Right panel: same as the left panel, but for the w2 − w3 versus w3 − w4 projection.