#unitytips: Hierarchy Window Group Header - http://diegogiacomelli.com.br/unitytips-hierarchy-window-group-header

HierarchyWindowGroupHeader.cs

using UnityEngine;
using UnityEditor;

/// <summary>
/// Hierarchy Window Group Header
/// http://diegogiacomelli.com.br/unitytips-hierarchy-window-group-header
/// </summary>
[InitializeOnLoad]
public static class HierarchyWindowGroupHeader
{
    static HierarchyWindowGroupHeader()
    {
        EditorApplication.hierarchyWindowItemOnGUI += HierarchyWindowItemOnGUI;
    }

    static void HierarchyWindowItemOnGUI(int instanceID, Rect selectionRect)
    {
        var gameObject = EditorUtility.InstanceIDToObject(instanceID) as GameObject;

        if (gameObject != null && gameObject.name.StartsWith("---", System.StringComparison.Ordinal))
        {
            EditorGUI.DrawRect(selectionRect, Color.gray);
            EditorGUI.DropShadowLabel(selectionRect, gameObject.name.Replace("-", "").ToUpperInvariant());
        }
    }
}

Thanks!
Upgraded with colors : https://gist.github.com/farukcan/fbed41147735c799466d95550c3216db

thanks for your work! forked to compile only in editor, in a namespace and simplified to 1 kind of header only
https://gist.github.com/ParkingLotGames/c17581afd0f754fd19f79bc82ca99bbc

Brilliant add-on to any project. Perfect 5/7.