How to Interact with Dialog Component

Hii i am using Dialog Component as Sub Window i want to set Header Height ,Background color

.vega-sub-window vaadin-dialog-overlay::part(header){
	background-color: ;

But i am not geeting please anyone can suggest what is wrong in it

Your problem is that vaadin-dialog-overlay is not probably a child of .vega-sub-window.

What you should do is to use setClassName in Java


And then you can use that

.my-overlay::part(header) {
   // ...