Redden means to become red or to cause something to turn red. It can describe a person’s face flushing with embarrassment or anger, as well as objects or surfaces taking on a red color. Key senses:

• Color change: something reddens when its color shifts toward red.
• Blushing/flush: a face reddens when embarassed, surprised, or flustered.
• Examples:
  • The sun reddens the sunset skies.
  • Her cheeks redden with embarrassment.
  • Leaves redden in autumn.