onTertiary property Null safety
A color that's clearly legible when drawn on tertiary.
To ensure that an app is accessible, a contrast ratio between tertiary and onTertiary of at least 4.5:1 is recommended. See www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast-contrast.html.
Implementation
Color get onTertiary => _onTertiary ?? onSecondary;