discoloration

This term describes a loss of original hue or the appearance of an unwanted stain, often carrying a negative connotation of decay, damage, or disease. It is frequently used in medical contexts to describe skin changes or in archival contexts to describe the aging of paper and fabric.

As an uncountable noun when referring to the general process of changing color, it does not typically take a plural form. However, it can be used as a countable noun when referring to specific, localized spots or patches of altered color on a surface.