Hi Brijesh,
Thanks for contacting syncfusion support.
Find the below sample to change the background color of parent row in SfTreeGrid.
We already have a sample to change the background color of parent row in SfTreeGrid in dashboard, please find the dashboard sample from the below mentioned location.
Sample Location: \{installed location}\Users \{Users.Login}\AppData\Local\Syncfusion\EssentialStudio\{installed Syncfusion ES build version}\WPF\SfGrid.WPF\Samples\ TreeGrid\LevelStylingDemo
Please let us know if you have any future assistance on this.
Regards,
Sathiyathanam