Background: The difference between colors of caries may give a primary diagnosis of the effected tooth as long as it is related to the ICDAS score and its microbial load. Aims: This study was conducted to investigate the relationship between the caries color to ICDAS score and its microbial load. Methods: Eighty children aged 4–7 years had caries primary molars were selected from the Pediatric Dental clinic, Faculty of Dentistry, Mansoura University. They were randomly divided into four groups based on color of caries of primary molars. Group A: Yellow color of caries, Group B: Light brown color of caries, Group C: Dark brown color of caries, Group D: Black color of caries. The classification was done by photographs illustrating the caries color, the eighty colors were classified into four main groups at the Faculty of fine art, to evaluate the relationship between International caries detection and assessment (ICDAS) and the microbial load according to caries color on the effected teeth. The data were collected, tabulated and statistically analysed.