Color usage patterns in book cover design from a complex-network perspective

Color is a fundamental element of visual design, shaping perception, cognition, and emotional response, and plays a crucial role in communicating cultural and genre-specific meanings. Here, we conduct a large-scale quantitative study of 32,614 book covers to examine how colors are systematically selected and combined in contemporary book cover design. By integrating statistical profiling, complex-network analysis, and generative simulation, we reveal both the structural organization and distributional regularities underlying color usage. Our analysis shows that most book covers employ between 5 and 8 distinct colors, reflecting a constrained yet non-random palette structure. Modeling colors as nodes in a weighted co-occurrence network uncovers four descriptive color-compositional groups, including saturated accent colors, cool core colors, warm bridge colors, and high-connectivity colors. Beyond individual frequencies, we find that the probability distribution of color-pair co-occurrence follows an exponential long-tailed decay, indicating the coexistence of a small number of conventional color combinations with a large diversity of rare and distinctive pairings. A generative simulation successfully reproduces this decay, suggesting that such scaling behavior emerges from constrained palette selection rather than statistical artifacts. Together, these findings reveal a latent “design grammar” governing book cover palettes, highlight parallels between visual culture and recurrent patterns observed in complex natural and social systems, and offer practical implications for publishing practice and AI-assisted design, where stability supports recognition while rare combinations enable aesthetic innovation.