A method of treating a body of recreational water with a composition which provides a visual cue to an end-user treating the recreational body of water signifying the effectiveness of the biocidal composition, the method comprises: administering to the body of water a biocidal amount of the composition comprising: at least 50% by weight of the composition of calcium hypochlorite particles; and an amount between 0.1% and 10% by weight of the composition of color emanating particles comprising, an oxidizable pigment, an oxidizable dye, a composition of an oxidizable pigment and a water soluble material comprising an inorganic salt, a gum or a resin, a composition of oxidizable dye and a water soluble material comprising an inorganic salt, a gum or a resin, or a mixture thereof; wherein the color emanating particles are suitable for releasing the oxidizable pigment and/or the oxidizable dye to the body of recreational water to provide a transient color emanating from the composition to the recreational water due to said pigment and/or dye being oxidized by said hypochlorite particles during dissolution of the composition in the body of recreational water, the transient color providing a visual cue signaling biocidal activity of the composition to an end-user; and wherein the composition is substantially free of surfactants to avoid foaming of the water; allowing the composition to dissolve or disperse in the water to release the pigment or dye into the body of water, providing a transient color emanating from the composition to the body of water during dissolution of the composition in the body of water, and detecting an absence of the transient color in the water thereby signaling to the end-user that the composition has been extinguished, and re-administering the composition to the water thereby replenishing the biocidal activity to the recreational water. at least 50% by weight of the composition of calcium hypochlorite particles; and an amount between 0.1% and 10% by weight of the composition of color emanating particles comprising, an oxidizable pigment, an oxidizable dye, a composition of an oxidizable pigment and a water soluble material comprising an inorganic salt, a gum or a resin, a composition of oxidizable dye and a water soluble material comprising an inorganic salt, a gum or a resin, or a mixture thereof; wherein the color emanating particles are suitable for releasing the oxidizable pigment and/or the oxidizable dye to the body of recreational water to provide a transient color emanating from the composition to the recreational water due to said pigment and/or dye being oxidized by said hypochlorite particles during dissolution of the composition in the body of recreational water, the transient color providing a visual cue signaling biocidal activity of the composition to an end-user; and wherein the composition is substantially free of surfactants to avoid foaming of the water; allowing the composition to dissolve or disperse in the water to release the pigment or dye into the body of water, providing a transient color emanating from the composition to the body of water during dissolution of the composition in the body of water, and detecting an absence of the transient color in the water thereby signaling to the end-user that the composition has been extinguished, and re-administering the composition to the water thereby replenishing the biocidal activity to the recreational water.