<p>Tuna is one of the most economically important seafood products, particularly in the sashimi market, where visual appeal, texture, and freshness are crucial to consumer acceptance. The bright red color of sashimi-grade tuna meat is governed by the redox state of myoglobin, which is highly susceptible to oxidation during post-harvest handling, processing, and storage. In addition, lipid and protein oxidation, microbial proliferation, and enzymatic degradation accelerate discoloration and lead to significant economic losses. This review explores the chemical and biochemical mechanisms underlying tuna discoloration, including brown discoloration and burnt tuna, with particular emphasis on myoglobin redox dynamics and its interplay with oxidative and microbial factors. Furthermore, natural additives, especially plant polyphenols, modified atmosphere packaging, and emerging non-thermal technologies such as ultraviolet-C irradiation and cold plasma are discussed as promising preservation strategies to retain color and maintain superior quality attributes. Future directions for integrating these hurdles, validating industrial scalability, and applying omics techniques to characterize key metabolites are also highlighted.</p> Graphical Abstract <p></p>