As a key figure of Post-Impressionism and the "father of modern painting", Paul Cézanne’s late portraits created from 1895 to 1906 mark the transformation of Western painting from traditional representational art to modern structural painting. Taking his portraits of this period as the research object, this paper starts with the transformation of his creative context and color cognition. It infers how the relevant works form four core creative paths: the construction of color harmony, the structural expression of color, the emotional projection of color, and the coordination between brushwork and color. On this basis, it analyzes the color expression forms and values of his painting language. Therefore, the color expression paths in Cézanne’s works—including independent form divorced from figurative imitation, pictorial structure based on geometric order, and expressive function carrying subjective emotion—have not only promoted the development of color language in modern oil painting, but also exerted a profound influence on later artists in his understanding and application of color expression forms.