SDSS g - r colour index vs. PA along the pseudo-ring. The red dots represent the g - r values obtained from the de-projected images. They are obtained by dividing g median flux to the corresponding r median flux of each aperture and converting these results to magnitudes. The pale blue dots correspond to the g - r colour index measured at a distance of r = 29.5 kpc (∼5′) on the sky. The green stripe sets the Green Valley interval that separates the red cloud (g − r > 0.75 mag) from the blue cloud (g − r < 0.60 mag) as defined in 4.3. The embedded figures correspond to typical flux × 10⁻¹⁰ histograms for two apertures from the SE region (PA = 70° − 258°, left panel) and the NW region (PA = 258° − 38°, right panel) separated by the vertical doted grey line.