MIR color-color diagram showing the Spitzer/IRAC colors of our confirmed MYSOs (blue dots) and the unconfirmed MYSO candidates (black dots). The Spitzer/IRAC photometric points of the MYSO candidates and S3-K are from Walborn et al. (2013). The photometric points of R135 are from the Spitzer/SAGE catalog (Meixner et al. 2006). Following the classification scheme of Gutermuth et al. (2009), we indicate the Class I and Class II regions and the regions where the Spitzer/IRAC colors might include unresolved knots of shock emission or resolved structured PAH emission.