Light influences secondary metabolite biosynthesis and quality, with varying effects depending on spectral composition. Therefore, more investigations into species-specific reactions to various light spectra are essential. In this investigation, the phytochemical characteristics of sage (Salvia officinalis L.) were investigated under six different light treatments. The plants were exposed to various light levels, such as white, blue, red, and mixtures of red and blue light (R70:B30, R50:B50, R30:B70) at the same intensity. Three replications were implemented in a completely randomized design. The variety of light spectra substantially affected the phytochemical characteristics of sage. The total flavonoid content decreased when red and blue lights were used separately, compared to when they were used simultaneously. The R70:B30 light treatment resulted in the maximum essential oil percentage (1.75% v/w). In the sage essential oil, 52 compounds were identified in total. The R70:B30 light treatment also greatly increased the production of important essential oil compounds, including camphor, α-pinene, camphene, borneol, and 1,8-cineole. The results of this study suggest that a ratio of 70% red and 30% blue is the most effective for improving phytochemical indices in the commercial production of sage in controlled conditions and advanced agricultural practices.