Ratio of X-ray flux (F_X) in 0.2–8.0 keV energy bands to optical flux (F_opt) versus hardness of the optical bands (left panel) or the X-ray bands (right panel). The F(P₁) and F(P₄) represent the observed fluxes in P₁ = 0.2 − 0.5 keV bands and P₄ = 2.0 − 5.0 keV bands, respectively. The circles and stars correspond to the identified CVs and CV candidates for eROSITA sources with the detection of the periodic signal in ZTF/TESS data. The solid and dashed lines in the left panel are taken from Galiullin et al. (2024a) and Rodriguez (2024b), respectively. The six sources enclosed by the black circle are low-luminosity candidates corresponding to those in Fig. 6 and Table 5. The second source is missing from the right panel as its F(P₄) is not measured, while the third source is missing because neither F(P₁) nor F(P₄) has been measured.