Relationship between galaxy V-band attenuation (A_V) and V − J reddening (A_V − A_J). The straight line shows the expected relation for a thin dust screen with a THEMIS-like extinction curve. The red circles correspond to the attenuation and reddening values in our fiducial dust model for massive, star-forming TNG100 galaxies. The blue star marker indicates the median attenuation and reddening values that the dust-free TNG100 galaxy population would need in order to reproduce the JWST/NIRCam data, while the orange cross marker indicates the actual median values of the TNG100 galaxies. To match the observational data, the attenuation-reddening relation must be almost as steep as in the dust screen model, which is not the case for the TNG100 galaxies postprocessed with dust radiative transfer.