onColor property

This getter returns appropriate contrast color based on a given color. It will return a color chosen according to the brightness of this color.

• The Color instance on which this getter is called is used to determine the brightness based on ThemeData.estimateBrightnessForColor method.
• If the estimated brightness is light, it will return a color Colors.black87.
• If the estimated brightness is not light (meaning it's dark), it will return Colors.white.