The cosmetics available today have attractive forms. Solid soap is a cosmetic that is widely used nowadays. To give it an appealing shape, some solid soaps are colored. There are two types of coloring agents there are natural and synthetic. Some synthetic dyes contain substances that are harmful to the body. This study aims to determine the effect of natural color from lerak fruit and evaluate the physical quality of yogurt whey solid soap. The research was conducted using a laboratory experimental method with yoghurt whey, lerak fruit, canola oil, palm oil, olive oil, VCO, NaOH, and essential oil to prepare of solid soap. The combination of yogurt whey and lerak fruit extract results in a good brown color. The hardened solid soap underwent organoleptic test, pH testing, foam height testing, moisture content testing, total fat testing, ethanol insoluble matter testing, free alkali testing, and chloride content testing. The results were analyzed using the shapiro wilk normality test, followed by one way ANOVA continued by Duncan’s test if the data were normally distributed. The yogurt whey solid soap formulation met the SNI standards except for the total fat test. In this test, variations in the yogurt whey content affected the results. Whey contains high sugar, which led to a decrease in the total fat results. The sugar in yogurt whey also influenced the color appearance of the solid soap. The solid soap with the most stable color in this study was F1, which contained 100% fresh cow’s milk and 0% whey.