The objective of this research study is to investigate the level of serotonin in the blood of people before and after a period of exposure to a yellow environment with yellow lighting to help improve their mild depression, emphasizing the last sentence of verse 69 of Surah Al-Baqarah. The current research project is a semi-experimental applied method. The statistical population in this research included 20 students of Kazeroon Azad University. Pearson's correlation coefficient and regression analysis were performed using SPSS software version 24 for data analysis, and for the normality of the data and comparing the averages in different stages, one-way ANOVA was performed. A confidence limit of 95% was considered in all tests. The findings of the study show that exposure to a yellow environment with yellow lighting increases the level of the serotonin neurotransmitter molecule. Finally, we came to the conclusion that there is a significant relationship between looking at yellow color and being under yellow light and the level of serotonin. Therefore, looking at yellow color and being under yellow light increases the level of serotonin and thus increases happiness in humans. This is in perfect agreement with the theme of verse 69 of Surah Al-Baqarah, which emphasizes the joyful nature of the yellow color.