Spectral energy distributions of the galaxies in our target sample, sorted by increasing observer-frame z − K color (rest-frame NUV  −  g at z  =  3.5). The observed photometry is shown with open black squares and gray error bars, and the best-fitting stellar continuum template from FAST++ obtained assuming z  =  z_phot is shown in gray in the background. For galaxies with a measured spectroscopic redshift (see Sect. 3.3), we display the best-fitting template at z  =  z_spec in orange, and the photometry corrected for emission line contamination with red squares.