Shen Quan was a professional folk flower-and-bird painter active in the Jiangnan region during the mid-Qing Dynasty, renowned for his gongbi style (meticulous brushwork) with heavy colors. He once sojourned in Japan for three years and was known as the "foremost imported painter." Focusing on color techniques as the core, this paper combines his extant works and cross-cultural context to analyze the color style of his flower-and-bird paintings and the Sino-Japanese color contexts, with particular attention to the evolution of his color techniques during his sojourn in Japan (1728-1731). In the Jiangnan region of the Qing Dynasty, Shen Quan emphasized the symbolic meaning of heavy colors; however, due to his departure from the literati painting aesthetic paradigm of "ink wash as elegance," his works were only regarded as a commercial tool to meet the needs of festival decorations. After his arrival in Japan, influenced by Japan’s native urban aesthetic, the realistic concept of Rangaku (Dutch Learning), and the Kano School, his color techniques shifted from auspicious symbolism to realism. His works not only retained the essence of China’s boneless painting technique but also integrated Japanese visual tastes and Western light-shadow logic. The essence of such differences and evolution lies in the dynamic adjustment of the perception of color functions in a cross-cultural context.