An HR diagram made using Gaia DR2 data. In red we show the absolute G magnitude, M_G, as a function of the blue-red colour, BP-RP, for AM CVns with known parallaxes. No reddening or extinction corrections have been applied to this figure. For comparison, in grey points we show a sample of essentially randomly selected main sequence stars which have a parallax better than 1 percent. For single white dwarfs shown as slightly larger grey points) we have used the sample of white dwarfs within 20 pc (Hollands et al. 2018). The majority of AM CVns appear to be brighter than the single white dwarf track, though some long-period systems lie on the track. A clear outlier is V407 Vul, which has BP-RP ≈ 1.5 through a combination of severe reddening and contamination from an unresolved nearby G-star.