Evolutionary tracks of the same 5 M_⊙ model stars reported in Fig. 4, based on the Blöcker (1995) and VW93 treatments of mass loss, are shown on the (F110W−F160W, F160W) (left panel) and ([3.6]−[4.5],[3.6]) (right panel) planes, with, respectively, black squares and red triangles. Magenta diamonds, orange circles and green pentagons refer to the evolution, respectively, of 4 M_⊙, 6 M_⊙ and 7 M_⊙ stars, where mass loss was described following VW93. Black crosses refer to the evolution of a 7 M_⊙ star, obtained with the Blöcker (1995) description of mass loss. Data points in the catalogue of M31 AGB stars by G22 are shown with grey points. Bright sources with F160W < 16 mag are shown with cyan points.