Light-emitting diode (LED) is an emerging technology with a high application prospect as a preservation technique for fruits and vegetables at the postharvest phase. This study investigates the effect of different LED wavelengths on the quality attributes of tomatoes during market-display conditions. Tomatoes were illuminated with different sets of LED treatments during the 5 days of storage: white, red-blue (5R:1B), and blue-red (5B:1R) LEDs before placing them in a market-displayed condition. Key quality indices, including colour, firmness, pH, brix, and weight, were monitored throughout the display period. Functional regression models of the quality index for the displayed period were established. Compared to the control, the 5B:1R LED treatment reduced tomato redness and overall colour change by 17.9%, suggesting a delayed ripening effect. Acid strength increased with a pH drop of 0.6, 0.5, and 0.1 units for 5B:1R, 5R:1B, and white LEDs relative to the control. Firmness improved by 43.1%, 31.4%, and 18.3% for 5B:1R, white, and 5R:1B treatments. Additionally, weight was retained more effectively, with increases of 30% and 4.9% for 5B:1R and 5R:1B LEDs over the control. A quadratic regression model effectively described changes and trends in the tomato market quality indices investigated. These findings provide a foundation for predictive modelling of tomato shelf-life and quality under LED treatments in market-displayed environments.