I'm not Youn, but I'll try a few words...
Use it to extract the bmp files from Reaper (Bitmap and icon folders). Use an image editor such as Photoshop or VCW VicMan's Photo Editor to modify the file. Open the new file in Resource Hacker or Restorator and replace the existing one with the new one.
But you know, the use of these tools will be short lived with Justin "providing a way to easily switch icons on the fly".
For more info you can check the SawStudio forum and search for shades. Resource Hacker or Restorator are used to skin Saw.
http://www.sawstudiouser.com/forums/index.php?
Here's a sample I'm working on.