How to set the background color or colored icon for the title bar at the top of the dialog box?

This is not that beautiful, it doesn't seem like what I want.
I hope the title bar above is colored.

var win = new Window("dialog", undefined, undefined, { resize: false });
win.orientation = "column";
win.alignChildren = "fill";

// Self drawn color title bar
var titleBar = win.add("panel", undefined, "TITLE");
titleBar.align = "fill";
// RGB 0~1
titleBar.graphics.backgroundColor = titleBar.graphics.newBrush(titleBar.graphics.BrushType.SOLID_COLOR, [0.2, 0.4, 0.8]);

// White text
titleBar.graphics.foregroundColor = titleBar.graphics.newPen(titleBar.graphics.PenType.SOLID_COLOR, [1, 1, 1], 1);
// Content area
var content = win.add("group");
content.add("statictext", undefined, "Here is the content");

// button
var btnGroup = win.add("group");
btnGroup.alignment = "center";
btnGroup.add("button", undefined, "OK");
btnGroup.add("button", undefined, "Cancel");

win.show();