Haliotis discus hannai is an important marine economic species in China.Its egg color was found to be associated with economic traits,which provides a new idea for breeding.However,the molecular mechanism of the egg-color formation has not been reported.Thus,the pigment composition and comparative transcriptome analyses of H.discus hannai with green and gray egg color were conducted using high-performance liquid chromatography(HPLC)and RNA-Seq methods.Results show that individuals with green and gray eggs both possess the fucoxanthin.Lutein existed in gray-egged individuals,but not in green-egged individuals.In transcriptome analysis,272 310 unigenes were received from 461 162 transcripts with a mean length of 985 bp and N50 of 1 524 bp,respectively.A total of 185 unigenes were identified as differentially expressed genes(DEGs).The DEGs involved in“flavin-containing compound metabolic process”,“melanosome”,“glutathione metabolism”,and“cytochrome b6f complex”were likely related to the formation of the egg color.Our results provide foundational information for the functional analysis of egg-color related genes and are beneficial to the selective breeding of H.discus hannai.