Flux-ratio diagrams based on the following lines: (a) Hul4 - Pfγ - Brα (Lenorzer’s); (b) Brα - Pfγ - Brγ (Granada’s – Persson & McGregor’s); (c) Pf18 - Brγ - Paβ; (d) Br12 - Paβ - Brγ. The symbols for each star are the same as in Fig. 4, but the colour represents the group the star belongs to: red symbols represent group I stars, blue symbols group II stars, and green symbols the transition group I-II. The grey symbols are for those stars without an L-band spectrum and no group classification. Zoomed-in views of the region where symbols overlap are plotted in panels c and d.