Upper panel: color–magnitude relation shown for the galaxies with effective radius R_e< 1.5 kpc for nucleated (blue squares) and non-nucleated galaxies (black points), and for the UDGs with R_e> 1.5 kpc, (red triangles) in our sample. The black line shows the linear least squares fit to the data points. The g′−r′ colors are measured with an elliptical aperture with semi major axis of R_e taken from GALFIT. The errorbars below the points show the size of the errors (Eq. (7)) along the color–magnitude relation. Lower panel: the color-surface brightness relation of the galaxies in our sample. The symbols are the same as in the upper plot.