Color-magnitude diagrams (CMDs) and color-color diagram (CCD) of the YJHK_S passbands for blazar candidates. The source VVV-J174555.13-362331.2 (RS17) is marked with a black circle. The magenta-cyan color map corresponds to the density of VVV objects lying within the positional uncertainty region of the UGS. In the CMDs, the dashed gray lines correspond to the color criteria of Baravalle et al. (2023). For the CCD, the solid gray lines and labeled regions are defined by Cioni et al. (2013).