Revision of Stellar Intrinsic Colors in the Infrared by the
  Spectroscopic Surveys
  Intrinsic colors of normal stars are derived in the popularly used infrared
bands involving the 2MASS/JHKs, WISE, Spitzer/IRAC and AKARI/S9W filters. Based
on three spectroscopic surveys -- LAMOST, RAVE and APOGEE, stars are classified
into groups of giants and dwarfs, as well as metal-normal and metal-poor stars.
An empirical analytical relation of the intrinsic color is obtained with
stellar effective temperature (Teff) for each group of stars after the
zero-reddening stars are selected from the blue edge in the $J-\lambda$ versus
(Teff) diagram. It is found that metallicity has little effect on the infrared
colors. In the near-infrared bands, our results agree with previous work. In
addition, the color indexes H-W2 and Ks-W1 that are taken as constant to
calculate interstellar extinction are discussed. The intrinsic color of M-type
stars are derived separately due to lack of accurate measurement of their
effective temperature.
