The experimental investigation of flame properties based on digital colour analysis has been conducted. In particular, the practicality of obtaining physical flame chemiluminescence characteristics through the inherent colour-filtering architecture employed in the digitisation of flame images was demonstrated. This is important as radical emission signals is an effective non-intrusive tool for deriving a number of useful combustion properties. In this study, a processing procedure was introduced which allows commercial digital colour camera to be transformed into a semi-quantitative device for radiation-based combustion diagnostics. Results have shown that the digitised primary colour outputs can be abstractly related to various emanating radicals in premixed CH(4) + air and C(2)H(4) + air flames. Both the RGB and HSV colour models were applied and each was found to be effective in tackling different issues in the overall make-up of the colour processing scheme. HSV-based numerical identity was able to recognise the appropriate RGB signal related to the radical chemiluminescence-induced digital colouration. From the recognised flame colour regime, the validity of the observed B and G signal correlation to emission characteristics of CH* and C(2)* radiation was conclusive by comparing with the results from the well-established spectrometry and optically filtered imaging methods. The abstract colour signals depicted similar radical chemiluminescence behaviour variations along with changes in equivalence ratio, reactant composition, and the increase of heat-release in the reactant flow. (C) 2010 Elsevier Ltd. All rights reserved.