onPrimary property
A color that is clearly legible when drawn on primary.
To ensure that an app is accessible, a contrast ratio of 4.5:1 for primary and onPrimary is recommended. See www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast-contrast.html.
If null, the on color is derived from the brightness of the primary color, and will be be black if it is light and white if it is dark.
Implementation
final Color? onPrimary;