(G – G_RVS) versus (V − G) relation for the stellar types (colour-coded) defined in Sect. 5. For clarity reasons, the dotted lines (metal-poor stars) have been slightly (+0.02) horizontally shifted and the dwarf and giant regimes separated. The (G – G_RVS) and (V − G) indexes only vary with the (B − V) colour index but the ranges covered in both axis are dependent on the metallicity. The crosses along the curves refer to (B − V) varying from 0.0 to 1.5 (step of 0.25) from bottom to top.