<p>The effect of green light on plant growth and development remains relatively understudied, with conflicting findings. This study investigated whether green light could substitute blue light in coleus (<i>Plectranthus scutellarioides</i>) and examined its effects on plant performance. A completely randomized design with six light treatments (red, green, and blue), T1 (10R:0G:0B), T2 (6R:0G:4B), T3 (6R:1G:3B), T4 (6R:2G:2B), T5 (6R:3G:1B), and T6 (6R:4G:0B), was applied with three replicates of six plants each, under controlled environments. Growth, leaf pattern area, color, chlorophyll content, and fluorescence were assessed. Plant height and internode length were highest under the 10R:0G:0B treatment, while the plants were most compact with smaller leaves in the 6R:0G:4B treatment. Green light promoted balanced growth, increased plant width (6R:2G:2B and 6R:3G:1B), and reduced excessive elongation. Blue light improved stem thickness and branching but reduced leaf area and shoot biomass at high levels. Chlorophyll fluorescence analysis showed that the combination of green and blue light enhanced photosynthetic efficiency. Additionally, blue light increased red pigmentation while reducing green and yellow tones. These results suggest that partial substitution of blue light with green light, particularly in T3 (6R:1G:3B) and T4 (6R:2G:2B), optimizes coleus morphology and photosynthesis without compromising structural integrity, providing a basis for optimizing light spectra in controlled environment cultivation.</p>