surfaceTintColor property
The color of the surface tint overlay applied to the material color to indicate elevation.
Material Design 3 introduced a new way for some components to indicate their elevation by using a surface tint color overlay on top of the base material color. This overlay is painted with an opacity that is related to the elevation of the material.
If ThemeData.useMaterial3 is false, then this property is not used.
If ThemeData.useMaterial3 is true and surfaceTintColor is not null and not Colors.transparent, then it will be used to overlay the base color with an opacity based on the elevation.
Otherwise, no surface tint will be applied.
See also:
ThemeData.useMaterial3, which turns this feature on. ElevationOverlay.applySurfaceTint, which is used to implement the tint. https://m3.material.io/styles/color/the-color-system/color-roles which specifies how the overlay is applied.
Implementation
final Color? surfaceTintColor;