The effect of light colour and light regime on growth and production of the thermostable C-phycocyanin (PC) by the thermophilic cyanobacterium Synechococcus 6715 in the tubular photobioreactor has been analysed. The highest specific growth rate (1.918 d⁻¹) and biomass concentration (5.11 g_VS ⋅L⁻¹) were observed under constant illumination of the red light. However, the PC concentration in volatile solids (e.g blue light 30.68 ± 0.8 mg_PC⋅g_VS⁻¹ PP and 21.7 ± 1 mg_PC⋅g_VS⁻¹ CI) as well as per photobioreactor unit volume (e.g red light 122.66 ± 2.28 mg_PC⋅L⁻¹ PP and 74.71 ± 8.43 mg_PC⋅L⁻¹ PP) was higher in the 16L:8D photoperiod. The obtained PC purity was higher in the case of photoperiod (≈1.5). PCC6715 lacks genes encoding phycoerythrins what suggests T1 type of pigmentation. Although changes in biomass pigmentation were not significant, the strain was able to adapt its photosystem what can be used in the optimization of PC production by application of different light colours.