Hi Ivan,
We are really sorry for very long delay in responding. DragSplitter could be accessed from the DockingManager.HostControl.Controls collections. Herewith I have attached the sample to change the Color of the DragSplitter. Please refer to attachment and let me know if it helps you.
http://websamples.syncfusion.com/samples/Tools.Windows/F59058/Main.htmThanks for using Syncfusion products.
Regards,
Murugan P.S