27 Which is the meaning of the colors in the electronic bands and phonon dispersions plots?

Different colors correspond to different irreducible representations of the point co-group of the k or q wavevector. To see the correspondence color-representation see the point_groups.pdf manual. The point group used for each k or q point is written in the thermo_pw output and also in the plot if you set enhance_plot=.TRUE.. In the output you can also find, close to each band energy or phonon frequency value, the name of the irreducible representation. Relevant character tables are given in the point_groups.pdf manual, in the thermo_pw output, or by the crystal_point_group.x tool.