In order to explore the role of red and blue light in the coloring process of tomato fruit, the micro tomato was planted with rock wool in an artificial light plant factory and irradiated with different lighting modes such as pure red light, combined red and blue light and alternating red/blue light. The reflection spectrum and hue index of tomato fruits at different development stages were analyzed to study the effects of red and blue irradiation modes on the spectral characteristics and coloring of tomato fruit. The results showed that: (1) The alternating irradiation mode of R6h/RB2h (pure red light/combined red and blue light, 6 h/2 h) was the most beneficial to the accumulation of the red pigments (e. g. β-carotene and lycopene) and the decomposition of chlorophyll, finally led to the earlier color conversion of tomato fruit; The effects of R (pure red light) was second only to R6h/RB2h; In contrast, the mixed irradiation mode of RB (combined red and blue light) was not conducive to the accumulation of red pigments and fruit coloring process of tomato fruit. (2) There are both synergistic enhancement effects and signal crosstalk weakening effects between red and blue light in promoting tomato fruit coloring. The alternated irradiation of R and RB may maximize the positive effects of single red light and mixed red and blue light in tomato fruit coloring. (3) The dynamics of pigment content reflected by spectral parameters such as Red/Green, MCARI, |PRI| of tomato fruit in the color conversion period displayed consistent with the color of tomato fruit reflected by Hue value, the reflection spectral characteristics of tomato fruit in this period were highly unified with peel coloring. The reflection spectrum of tomato fruit in the color conversion period can better reflect the degree and process of tomato fruit coloring.