Left: part of an HST image of the galaxy cluster MACS J1149+2223, where the four objects used to extract SEDs are indicated with red contours. Middle: extracted SEDs. Each curve corresponds to the SEDs of the galaxies circled in red in the first panel. Right: simulated SEDs. The seven red SEDs are used to produce the upper row of galaxies in Fig. 6. The blue SEDs correspond to the lower row of galaxies (see text).