Athletic field paints are routinely applied to turf surfaces to demarcate sports fields. Although they do not typically cause acute injury, field managers routinely notice chronic declines in turfgrass health and quality from repeated applications. This study was conducted to determine the impacts of athletic field paint on spectral quality within the turfgrass canopy and associated photosynthesis. Growth chamber experiments were designed to evaluate the effects of red and white athletic field paint (no dilution and 1:1 dilution with water) on net canopy photosynthesis (Pn) of perennial ryegrass (Lolium perenne). Paint treatments were applied weekly for six weeks with net canopy photosynthesis recorded 24 hours after each application using a portable gas exchange system. Additional experiments were conducted using a spectroradiometer and integrating sphere to evaluate reflection, absorption, and transmission of light based on paint color, dilution, and thickness. Narrow-band spectral data collected were 410, 430, 640, and 660 nm ±10 nm while broad-band data collected were 400-500, 600-700, and 400-700 nm.  Over a six week period all paint treatments reduced Pn with treatment effects being dependent upon color (P ≤ 0.0001) and dilution (P ≤ 0.0001). Red non-diluted paint produced a 75% reduction in canopy photosynthesis over six weeks while white 1:1 diluted paint only produced a 19% reduction. Broadband spectroradiometer data suggests this is likely due to reductions in PAR with red paint absorbing 51% of incident PAR while only transmitting and reflecting 6% and 43%, respectively. White paint transmitted 5% of PAR while reflecting 95%. Narrow-band responses varied by wavelength. Alterations in light spectral quality as a result of athletic field paint applications can significantly impact PAR available for turfgrass photosynthesis that may result in a decline in turfgrass quality.