Colorants in turf are more closely related to pigments and dyes. The major difference between between pigments and dyes are their solubility (dissolve in liquid). Pigments are relatively insoluble while dyes are soluble. Pigments specifically, and to some extent dyes are substances that absorb, transmit, and reflect specific light wavelengths . There are a number of turf colorants on the market worldwide. In the United States alone there are over 25 colorants on the market. Colorants are normally broken down by UV light.
In most cases dyes and pigments are added to actively growing, damaged or discolored turf. Markers, for example are colorants that are added to a spray tank to mark the length and width of a sprayer pattern reducing the likelihood of skips are overlap. Dyes and pigments maybe added to a product or a tank mixture to provide color to a turf that is showing stress symptoms. With certain colorants research is showing they may contribute to overall turf health. The potential benefits lies in repeated applications on actively growing turf. How long a colorant will last depends on the product, and environmental conditions, and the growth rate but most last between 20 and 60 days.
Video: Late winter application of a pigment to an athletic field.