Berthellina citrina (Rüppell and Leuckart, 1828) is a common Pleurobranchid gastropod in the intertidal area of the Red Sea. It has distinct color pattern variation from pale yellow, orange to red. The present study aimed to evaluate whether the variation of these color patterns are due to polymorphism, or may be speciation. Anatomically, the three color patterns showed variations in their digestive systems especially in the shape of the crop, stomach and the intestine. However, the reproductive system showed variations in the prostate gland, penis, the connection of receptaculum seminis with busra copulatrix and the convolution of both distal part of vas deference and penial gland. Statistically, morphometric analysis, linear regression and discrimination function using length and width measurements of the main taxonomic characters; shells, buccal masses, radulae and jaws separated the red color pattern from the other two color patterns. Also, cluster analysis of the three color patterns based on length and width ratios of the previous taxonomic characters revealed that, the red color pattern comprised a separated group and the pale yellow and orange color patterns are very close. So, the present data revealed that there is a significance variations between the orange and pale yellow color pattern from the red color one and these may be led to isolation of the red color pattern as a separate species.