UVJ diagram sampling the parameter space of the DirtyGrid geometrical models. The JWST/NIRCam distribution for massive galaxies (M_⋆ ≥ 10¹¹ M_⊙) is also shown in each panel by the grey contours. The different columns correspond to different DirtyGrid geometries, which are schematically depicted at the top of each column. The upper panels show the results using a constant SFH, while the lower panels correspond to a single-burst SFH. Stellar ages and dust optical depths of the DirtyGrid models are indicated by the various markers and colors, respectively. We keep the stellar metallicity fixed at a metal mass fraction of 0.02. Furthermore, we use a constant stellar mass of 10⁹ M_⊙ and a fixed Milky-Way-like dust extinction curve. As reference, we also show the dust-free colors of a BPASS simple stellar population (SSP) with a metal mass fraction of 0.02 in one panel. We find that young stellar populations with a single-burst SFH and a homogeneous shell geometry (lower row, third column) can match the UVJ colors of massive, star-forming JWST/NIRCam galaxies at intermediate V-band optical depths (τ_V ∼ 10^0.5).