The indigo leaf contains the precursor of two dyes, indigo and indirubin. Indigo is the blue of blue jeans and is the usual product of pigment extraction. With different chemistry, the components in the leaf an the chemicals added can cause the reaction to produce the indirubin pink color.
I do this with the freshly picked leaves of indigo plants I grow in my home dye patch. Many more leaves are required to obtain the pink than for the blue. The process is little know, so the color is rarely found in commerce.
You should also know that indirubin is ant-leukemic, and there is research on many other cancers. Whether an indirubin dyed scarf benefits the wearer may be known by somebody, but not by me. The skin, after all, is the largest organ.