The work aims to analyze the two-level color semantics of the bus service system APP, namely extended and connotative meanings, from the perspective of color semantics and combined with psychology, semiotics, product semantics and other knowledge. Based on semiotic coding and decoding theory, the semantic composition, semantic communication and semantic design of color design in bus service APP are carried out to obtain the color design framework. The extended semantics of the color symbols are expressed as “explicit” relationships while the bus service system APP directly explains the content. The intentional semantics is the second level and expressed as the “potential” relationship, which indirectly illustrates the psychological, social or cultural meanings of the content other than the color content in the bus service system APP. After analyzing the designer-user-color relationships in the color semantic elements of the bus service system APP, the process of encoding and decoding is completed through design coding, use of decoding, and decoding and feedback of the final effect. By analyzing the user’s perception model of color semantics and color combination, the user??s semantic decoding ideas when accepting color symbols are analyzed. The color design method of the bus service system APP is studied to improve the user??s efficiency and quality of color semantic decoding and provide a theoretical basis for the color design of the bus service system APP.