Yes that is fairly straight forward to do.
You need to make a two state LED graphic. For example of what I mean look in the bitmaps / millBitMaps folder and look at "BlueLED.png" or "conditions.png"
When you have made your button graphic then you can assign it in Screen4 as the image to use for your LED. Set it as "Red/Green Flashing"
Now to make that LED appear and work as a button on screen you place an "Image Button" over the top of it.
And here is the trick.....make yourself a transparent png image and use that as the image for the button.
If you don't do the last bit the flashing LED won't work. Don't ask me why. I don't know. It is one of Screen4's many little quirks.