Tetrastigma hemsleyanum is a traditional Chinese medicine herb, commonly used for its anti-inflammatory and antitumor properties. Flavonoids are the main functional constituents of T. hemsleyanum, and their production in the herb is affected by light quality. T. hemsleyanum is a shade-loving plant and is usually covered by black shade nets during cultivation. However, there are only a few studies on the effects of using color films on growth and flavonoid synthesis in T. hemsleyanum. In this study, we measured the influence of five different color films on growth indexes—sugar, soluble amino acid, soluble protein, and flavonoid content—and flavonoid-synthesizing enzyme activities in T. hemsleyanum. The films used were colorless plastic film as the control group (CK-W), red film (RF), yellow film (YF), green film (GF), and blue film (BF). BF promoted plant growth and increased yield, as evidenced by the highest growth indexes, soluble amino acid content, and chalcone isomerase (CHI) enzyme activity. RF increased the content of secondary metabolites, thereby enhancing herb quality, as evidenced by the highest phenylalanine ammonia lyase (PAL) activity and increased flavonoid content.