This study is conducted to improve growth performance, breast meat characteristics, welfare, and immunity level of broiler chickens by using a combination of monochromatic LED light in the early and later periods of the rearing. A total of 576 one-day old mixed sexes broiler chickens (ROSS 308) were randomly assigned to one of 4 treatments: 1) White fluorescent light (Control, WF), 2) Green LED light (G), 3) Blue LED light (B) and 4) Green-Blue LED combination light (G-B) (green light for first 3 weeks, switching to blue light for remaining 3 weeks). Body weights (BW), body weights gain (BWG), feed intake (FI), feed conversion ratio (FCR) and mortality rates were determined. In addition, on d 39, gait score and at 21 and 40 d of age, tonic immobility (TI) duration and at 28 and 40 d for immunoglobulin G (IgG) in serum and at d 42 of age, pectoral muscle quality and tibia bone characteristics were determined. The results showed that birds under Y-M had significantly higher CA in the first 21 days than these of BF and M and in the last 3 weeks than the broilers in the BF and G. At the end of the experiment, it was revealed that the B and G-B groups consumed more feed than the other groups. FCR, mortality rates and TI duration in broilers were not affected by light treatments. Light affected the gait score which is a welfare indicator in broilers was affected and G group had the worst gait score. Light affected values of pH24, b* and water-holding capacity in the breast muscle and the lowest pH24 value appeared in G-B group. On 40th day of the trial, although the IgG levels in all the treatment groups decreased according to the 28th day, the IgG level of G-B group was found higher than the other groups. In conclusion, the present study shows that in chickens, the monochromatic G-B combination had a positive effect on the growing and especially the high level of IgG determined in the blood serum showed that it can be effective in development of a strong immunity.