Runaway electron (RE) mitigation by gas injection of argon (Ar) and deuterium (D) has been investigated in the COMPASS tokamak in past campaigns [1,2]. Ionisation or excitation of Ar and D due to the presence of the RE beam leads to subsequent recombination or deexcitation. Part of the emitted radiation is captured by rapid ($5\,$kfps) visible color imaging systems. The presence of ArII and D bulk plasma during a singular discharge is characterized by the dominance of the blue ($\sim450\,$nm) or red spectral bands ($\sim650\,$nm), respectively. Furthermore, in the electron temperature range of $T_{e} \in (0,2)\,$eV, the fractional abundance of ArII increases with temperature while the one of D decreases. Making the radiation incident on the camera's filters dependent on temperature. On the other hand, the light emission in the poloidal plane is reconstructed by tomographic inversion assuming toroidal symmetry of the RE beam. Different algorithms were used [3,4]. Each of the methods presents advantages. On top of that, the effect of toroidal asymmetry, due to inhomogeneous gas injection and reflections, plays a role in the accuracy of the reconstructions. Finally, the inverted planes together with estimation of $T_{e}$ as a function of fractional abundance and light emission give a temporal evolution of bulk plasma $T_{e}$, $n_{e}$, $n_{D}$ and $n_{ArII}$ profiles. [1] J Mlynar et al. “Runaway electron experiments at COMPASS in support of the EUROfusion ITER physics research”. In: (2018). doi: 10.1088/1361-6587/aae04a. [2] Ondˇrej Ficker. “Generation, losses and detection of runaway electrons in tokamaks”.MA thesis. Czech Technical University in Prague, 2015. [3] Jordan Cavalier et al. “Tomographic reconstruction of tokamak edge turbulence from single visible camera data and automatic turbulence structure tracking”. In: (2019). doi: 10.1088/1741-4326/ab0d4c. [4] J. Svoboda et al. “Tomotok: python package for tomography of tokamak plasma radiation”. In: (2021). doi: 10.1088/1748-0221/16/12/C12015