You are correct that the color on the tips is the temp range
Blue - 325°C - 358°C
Yellow - 350°C - 398°C
Red - 420°C - 475°C
As for which series of tips
P - work with MFR-PS1100, MFR-PS2200, MFR-PS1K, MFR-PS2K
S - SP200, MFR-PS1100, MFR-PS2200 (SSC Tips)
M - MX-500, MX-5000, MX-5200
K - The K series only works on the Thermaltronics systems and only works.