Magnitude–colour diagrams showing the magnitude of all sources from the sample obtained in this work (black dots) only detected in the first three wavelength IRAC bands (i.e., 3.6, 4.5 and 5.8 μm). Panels on the same row display, from top to bottom, the measurements for these sources in the 3.6, 4.5, and 5.8 μm bands, respectively, plotted as a function of [4.5] – [5.8]. In the left column panels, they are overlaid with all sources from GLIMPSE II (red dots) at least detected in the three shorter wavelength bands. The green dots in the right column panels are the sources remaining from our photometry list after removal of those contaminated by PAH emission. Only objects with photometric errors <0.3 mag in the three shorter wavelength bands are plotted.