This study was aimed to evaluate the impact of different monochromatic LED light colour (white ‘WL’, green ‘GL’, blue ‘BL’ and mixed green and blue ‘GL BL’) and two levels of light intensity (5 lx and 20 lx) on growth performance, physiological responses (haematological and biochemical), behaviour and fear reactions in broiler. A 4 2 factorial treatment structure was used to evaluate the impact of 4 LED light colours (WL, GL, BL and GL BL) and 2 levels of light intensity (5 lx and 20 lx) in triplicates. One-day-old Cobb Avian-48 chicks (N¼ 384, 36.29 ± 0.092 g) were used. Results revealed a significant effect of light colour on performance (final weight, weight gain and feed conversion ratio [FCR]), haematological parameters (haemoglobin, RBCs, PCV, TLC and H/L ratio), biochemical parameters (TP, albumin (AL), and AL/globulin (GL) ratio), tonic immobility (TI) duration and open field (OF) test (latency to first step, mobility duration, immobility duration, immobility sitting, immobility standing, pecking and dropping) with the best results observed in GL BL. Light intensity had no effects on studied parameters except for H/L ratio, TI duration, latency to first step, immobility sitting, immobility standing and pecking with better findings detected in 5 lx. There was a significant light colour light intensity interaction on final weight, weight gain, AL, TI duration, mobility duration, immobility duration, immobility sitting, immobility standing and pecking. Conclusively, monochromatic LED light (GL BL, BL and GL) particularly of low intensity could be a source of light in broiler houses that might have the potential to improve broiler welfare.