Why are colored and white items washed separately?

In physics there is such a concept – diffusion. Diffusion is the mutual penetration of particles of one substance into another. Such diffusion processes take place during washing. Colored laundry contains dyes. Dye molecules, when washed together with colored and white linen, penetrate into the fabric of white linen and remain there. In order to maintain the proper appearance of white items that do not contain dye, these items must be washed separately from colored items.