Upper panel: (I,V − I) Danish instrumental CMD of the field around MOA-2007-BLG-197, not corrected for interstellar extinction. The red point marks the position of the RCG. The magnitude of the microlensing target is in blue (i.e. magnified source, lens and blended light). The orange point corresponds to the source alone. Lower panel: empirical linear relation between instrumental colours (I_DK − I_MOA) and (V − I)_DK (red and green points are astrometric matches that are uncrowded in the MOA image; after sigma-clipping, only red points are used for the fit).