Diagram of  [4.6]  −  [12]  vs.  [12]  −  [22] . The black dots represent 3% of all objects that have been catalogued in all the WISE and 2MASS bands. Larger green dots represent bright known Galactic RCB stars (the two outliers are discussed in the text); red dots correspond to the Galactic RCBs found toward the bulge (with a majority located inside the bulge) (Tisserand et al. 2008; Zaniewski et al. 2005); blue dots are 4 RCB stars located in the south-eastern area of the Large Magellanic Cloud. The purple stars correspond to the 5 known HdC stars and the circles to DYPer type stars with a colour coding identical to RCB stars. The red lines represent the selection cuts used in the analysis.