WD effective temperatures (from literature) as a function of Gaia colours BP−RP for known (and confirmed) DA (filled red squares) and non-DA (open red squares) WDs. The solid and dashed red lines show the 5th order polynomial fit for these objects excluding CA403 (=WD 1943+163; see text) and its extrapolations. Black open lozenges mark the effective temperatures of new (and confirmed) WDs corresponding to their initial spectroscopic classification (Sect. 4) as a function of their Gaia colours. Black filled lozenges mark their newly derived effective temperatures using the fit with known WDs (error bars are explained in the text). The fitted values of new WDs are marked by their CA names.