Editing Drawables
There are many types of drawables. One of this, res/drawables, contains a bunch of xml. You generally don't need to edit this (as you should have changed everything already). The next part is the drawables mdpi, hdpi, and xhdpi (there is also ldpi and xxhdpi for others). These ones contain lots and lots of images. It is generally not hard to edit them, but somewhat time consuming. You can go ahead and right click on the hdpi one and open it with file explorer. This one (high density) generally has most of the pictures. Get an image editing software like photoshop or gimp (free!) and do as you wish. For those of you who are blacking out apps, you might want to replicate the dark pngs to the light ones and make backgrounds dark. Everything is truly up to you. However, there is one thing that we need to watch out for...
Editing 9.png
I'm going to make this really short, since we aren't really making 9.png's ourselves. Just make sure that the black bars on the side remain black when you are done. Even the darkest shade of grey will screw it up. If you want to know more though, check this out (scroll down)
Oh, and did I mention what happens if you do this wrong? This....
Oh, and did I mention what happens if you do this wrong? This....