A doubled haploid (DH) population consisting of 240 strains of Pyropia haitanensis was constructed using the heterozygous filament derived from the cross between the wild-type strain (W, ♀) and the red mutant (R, ♂) in the experiment. The correlation of blade color with the five quantitative traits of length, width, blade thickness, protoplast size and cell wall thickness of gametophytic blades was subsequently analyzed. The results showed that the phenotypic values of the five traits were normally distributed in different color groups (the wild-type group and the red-type group). The variation coefficient of each trait ranged from 10.02% to 43.73%, and the variation coefficient of length was the largest. The phenotypic values of each trait showed significant differences among different color groups (P < 0.01). Compared with the wild-type group, the blades of red-type group had longer length, narrower width, thinner blade, smaller protoplast and thinner cell wall. The correlation degrees between color and each trait were ranked in the order of blade thickness > cell wall thickness > protoplast size > length > width. In addition, the heritability order of each trait was presented as length > protoplast size > blade thickness > cell wall thickness > width, and the heritability in the wild-type group was higher than that in the red-type group. The genes controlling the same economic trait were different in different color groups, and the genes controlling the length trait were the most different. This study provides reference for developing new varieties with compound economic traits in P. haitanensis.