Colour fastness is a term—used in the dyeing of textile materials—that characterizes a material's colour's resistance to fading or running. Colour fastness is the property of dyes and it is directly proportional to the binding force between photochromic dye and the fibre. The colour fastness may also be affected by processing techniques and choice of chemicals and auxiliaries.
The term is usually used in the context of clothes. In general, clothing should be tested for colour fastness before using bleach or other cleaning products. It can also apply to upholstery fabrics.