Distribution of giants on the CaMD diagram in a mock realisation of the Milky Way using the Galaxia code (see Appendix C.2). The top panel shows M_G vs Gaia colours, while the bottom panel shows M_W1 versus AllWISE colours. The RC is marked by the black contours. The marginalised histogram (normalised) for the x (top sub panel) and y (right sub panel) axes are also shown. For the RC, both M_G and M_W1 can be approximated by a quasi-Gaussian as is shown by the red curves on the right insets.