Hi Dewa,
By default, we have mapped the app's color scheme to
the SfDateRangePicker. We suspect that you have modified the
default theme data affecting the SfDateRangePickerTheme. To resolve this issue, we recommend
using the SfDateRangePickerTheme to customize the theme. We have
shared a user guide and documentation for the SfDateRangePickerTheme, along with a live sample that
includes the default theme data, for your reference.
UG Link: https://pub.dev/documentation/syncfusion_flutter_core/latest/theme/SfDateRangePickerTheme-class.html
Live sample: https://flutter.syncfusion.com/#/date-range-picker/getting-started
If you still facing any issue, please provide a reproduce
sample it will be more helpful to us to provide a solution sooner.
Regards,
Preethika Selvam.