u − i color versus the i-band absolute magnitude of the sample in comparison with the grid of colors from the models discussed in Sects. 6.1 and 6.2. The UDGs and the diffuse galaxy subsamples are marked with the filled red and open blue circles, respectively. The black star symbols are the sources detected in Hα. Sources with only an upper or lower limit in the color are excluded from the plot. The blue grid corresponds to galaxies without any environmental interaction (non-RPS models; see Sect. 6.1). The green, red, and black grids correspond to models with an RPS event at different epochs (ongoing, 1 Gyr ago, and 2 Gyr ago, respectively). The black labels marked along the blue are the different λ (0.01 to 0.80) and V_C (20 km s⁻¹ to 600 km s⁻¹) values of the models, as given in Table 3. The dotted and solid lines in the grids give the variation for a fixed λ and V_C, respectively.