The purpose of study was to develop new dental plaque disclosants which could replace erythrosine. Three food coloring agents(Red No.40, Blue No.1, and Mixed Green), erythrosine and fluorescein were tested for their color difference, antibacterial property, and biocompatibility. Color difference of Red No.40 was greater than that of erythrosine as concentration of solution increased. Color differences of Blue No.1 and Mixed Green were smaller than that of red dyes. Erythrosine showed obvious antibacterial property, but food coloring agents showed almost no antibacterial property. The taste and sensation of erythrosine was the worst, and the taste of Red No.40 and the sensation of Mixed Green were the most tolerable. Erythrosine stained dental plaque and oral soft tissue most deeply and long, and Blue No.1 was the next in the depth and longevity of stain.