1. present participle of discolour; to change or spoil the colour of something; to stain or cause to lose original colour
Usage: British spelling (American: discoloring); commonly used in passive voice

1. the process or result of changing colour; a stain or mark that spoils appearance
Usage: gerund form; often used as an uncountable noun

Examples

• The water was discolouring the white fabric.
• Years of sun exposure caused discolouring of the old photograph.
• Rust is discolouring the metal gate.
• The wine spill left a discolouring mark on the carpet.
• Discolouring of teeth can result from certain medications.
• The artist noticed discolouring on the canvas after storage.
• Chlorine was discolouring her hair.
• Mold growth is discolouring the bathroom tiles.