By squeezing the fresh leaves of sacatinta (Justicia spicigera Schlecht), which grows in Central America, a brilliant purple solution is obtained. Thus produced colorant will dye cotton fabrics blue. Herein, the properties and dyeing behavior of the colorant from the plant, which is unfamiliar to Japanese, were investigated. The color of the colorant which was rapidly developed from the colorless solution of the leaves was stable to alkali but changed with acid. The color of the solution faded under a sealed condition and reappeared when exposed to air, indicating that the colorant is reduced by some reducing substance in the leaves. However, the colorless precursor in the fresh leaves was found not to be the reduced form of the colorant. A variety of fabrics, including cotton, could be dyed blue to purple with the squeeze of sacatinta. Three colorants were detected from the extract of the dyed fabrics by HPLC analysis.