Spectral, grey-scale and colour chemiluminescence measurements of C 2* and CH* radicals' emission are carried out on the flame front of a methane-air premixed flame at different equivalence ratios. To this purpose, properly spatially resolved optical equipment has been implemented in order to reduce the background emission from other burned gas regions. The grey-scale (ICCD + interference filters) and RGB colour (commercial digital camera) approaches have been compared in order to find a correspondence between the C2* and the green component, as well as the CH* and the blue component of the emission intensities. The C2*/ CH* chemiluminescence ratio has been investigated at different equivalence ratios and a good correlation has been obtained, showing the possibility of sensing the equivalence ratio in practical systems. The grey-scale and colour chemiluminescence analysis has then been applied to a meso-scale not premixed swirl combustor fuelled with a methane-air mixture and operating at 0.3 MPa. 2D results are presented and discussed in this work.