Multi-frequency light curves for all the sources monitored by the F-GAMMA programme (“f”, “s1”, “s2”, and “old”) and the F-GAMMA-Planck MoU. The lower panel in each frame shows the evolution of the low (2.64, 4.85 and 8.35 GHz), mid-band (8.35, 10.45 and 14.6 GHz), and high-band (14.6, 23.05, 32, 43 GHz) spectral index. Only spectral index estimates from at least three frequencies are shown. Connecting lines have been used to guide the eye.