Spark-processing has been shown recently to generate a silicon-based substance which intensely photoluminesces in the UV/blue or green spectral range, depending on whether the preparation was performed in flowing or stagnant air, respectively. This study reports about significant differences for the radiative properties of spark-processed silicon after preparations in oxygen, nitrogen, and mixtures of both gases. Whereas there is essentially no photoluminescence (PL) after processing in pure nitrogen, an orange PL band at 1.89 eV occurs after preparation in pure oxygen. The orange PL degrades with time and when exposed to laser light. Furthermore, it switches immediately to a more intense blue emission centered at 2.61 eV when the sample is subjected to lower gas pressures. A similar 2.6 eV PL is observed after heat treatments up to 350°C. If, however, spark-processing of Si is carried out in nitrogen and oxygen is added, a green PL arises, centered at 2.35 eV. Moreover, for a volume ratio of about 1:1 N2/O2 a PL band at 3.22 eV emerges, superimposing the green emission. Both bands are about two orders of magnitude more intense than the orange PL, when prepared under otherwise identical processing conditions.