Effects of supplementing green light to red and blue light on the growth and yield of lettuce in plant factories

•Lettuce growth and yield improved by the addition of green light.•30 µmol m−2 s−1 of red and blue light supplemented with green light increase lettuce yield.•Supplementation of higher red and blue light with green light (≥50 μmol m−² s−1) hampers growth of lettuce.•The suitable photosynthetic photon flux density (PPFD) of red, green and blue light would be 211:30:53 (μmol m−² s−1) for lettuce production.