pEW diagram of Ti IIλ4000 plotted against the color stretch parameter s_BV showing the three subtypes 91bg-like (red), 86G-like (green), and 04gs-like (orange) from our subluminous sample, along with normal SNe Ia with s_BV < 0.8 (grey) as distinguished different SNIa populations based on their spectral characteristics and color evolution. The shaded regions around each subtype indicate the confidence levels (1σ and 2σ ) of their distributions in the pEW–s_BV plane. Additionally, the 4 91bg-like SNe Ia labeled as silver candidates in (blue) are plotted and re-classified with respect to their distance to maximum of the KDE distributions of the three SN Ia populations (91bg-like, 86G-like, and 04gs-like). The cumulative distributions for all different SN Ia populations are shown in the right panel.