Why can’t a fabric dyed with unstable dyes be kept in contact with light-colored laundry when wet?

Fabric dyed with unstable dyes should not be kept in contact with light-colored linen when wet, because light-colored fabric may stain. Two fabrics are wet, the dye diffuses from one fabric to another. The dye molecules from one tissue penetrate into the light tissue, and the longer the contact time of the tissues, the more molecules will pass into the other tissue and the more it will be dyed dark.