Colour (G_RP − K_s), corrected for interstellar extinction, plotted as a function of pulsation period. Circles represent the M-type LPVs of our sample. Triangles are the large-period small-amplitude group in our sample seen in Fig. 2. Filled circles are the discovered distant LPVs listed in Table 3. The LPVs of the globular clusters ω Cen ([Fe/H] = −1.6) and 47 Tuc ([Fe/H] = −0.70) are shown for comparison, and are indicated by plus signs and crosses, respectively. Note that a few GC LPVs with log(P) > 2.1 are located along the rising red main group. Uncertainties are comparable to symbol size.