K − [22] vs P diagram of the 1600 stars unsaturated in the K and [22] bands and with a known spectral type; see the legend for identification of the spectral types and the number of Miras in each group. The solid orange line is the relation given by Eq. (2) that best separates Group S and A Miras. The dashed lines are the linear least-square fits to the four groups of Miras listed in Table 4 (black: M(NB), red: M(B), green: S, blue: C Miras). The dotted blue and red lines indicate the limits of K − [22] = 0.55 and 0.85.