Colour-magnitude diagram defined by the F336W and F475W filters for the stars in the PHATTER catalogue(Williams et al. 2021). The red rectangle denotes the selection cuts for young main sequence stars: F475W < 21 and −2< F336W−F475W <  − 1. Orange curves are evolutionary tracks (Choi et al. 2016) along the main sequence and the red giant branch for stars of masses in the range 10 to 50 M_⊙, as labelled in the figure.