How do you pinch purple presperation stains from a black dress? My sister washed her black dress and very soon she has...

My sister washed her black dress and very soon she has a violet-purple stain lower than the underarmes where she prespired. How do you remove them?
Answers:    Becareful of some dyes- capture a natural dye from the condition food store- some are cancer- causing!
You will own to dye the dress black to get rid of them.