The fruits of Solanum lycopersicum L. cultivar “Microtom” are a powerful source of antioxidants. We investigated whether two light-quality regimes, i.e., fluorescent white (FL) and red-blue (RB), influenced the antioxidant composition in such fruits, and assessed the potential radioprotective properties of their extracts on normal human cells exposed to clinical photons as used in cancer radiotherapy (RT). Increasing normal-tissue tolerance to radiation is critical for reducing the risk of RT-associated sequelae. Biochemical characterization showed that RB enhanced the content of antioxidant phytochemicals (i.e., polyphenols, flavonoids, total carotenoids, lycopene), while FL promoted ascorbic acid synthesis. Initially tested at 200 µg/mL, RB-derived extracts decreased radiation-induced DNA damage as measured by the cytokinesis-block micronucleus (CBMN) assay in epidermal HaCaT cells. Both RB and FL regimes were subsequently studied in MCF-10A breast cancer (BC) cells, a model of normal-tissue radioresponse in BC RT, using extracts at 100 and 200 µg/mL and also evaluating oxidative stress by a ROS detection assay. Both FL and RB afforded radioprotection. However, RB suppressed radiation-induced MN formation and oxidative stress to a greater extent compared to FL. Therefore, modulation of light-quality regimes represents an innovative approach for developing radionutraceuticals with potential benefits for RT patients.