Colour-colour diagrams for the two fields observed in 2018 (left) and the two observed in 2020 (right). Grey dots are all stars with PIGS photometry in the targeted fields passing the respective Sgr selection criteria for those years (see Sect. 2.1) and G < 17. Black dots in the top row are all observed AAT stars in these fields, coloured small dots in the bottom panel are good quality AAT stars coloured by spectroscopic metallicity. Large dots denote Yoon et al. (2016) CEMP stars with logg < 2.5 and −3 < [Fe/H] < −2.0. Colour coding in the top row is [C/Fe], in the bottom is [Fe/H]. Vertical lines indicate colour cuts applied. The stars within the pink circles in the top left and right panels are discussed in Sect. 5.2 (in the right-hand panel, it is at (x,y) ∼ (1.4,−1.3)).