A dried stain is like a smoking addiction. It's pretty hard to kick. A spot on white clothes though, can sometimes be removed by squeezing lemon juice onto it and laying the garment in the sun. The sun and the lemon juice will act as bleaching agents. Once the stain is gone, make sure you rinse the garment before washing it with other clothes; a bleach mark on a colored garment is the most stubborn stain of all.