If you just want to change the image sizes, open the apk with 7-zip or another good archive prog, but do not extract it, just open it. Then swap out the images you need to with their smaller conversions. Close the file, and resign it, then install.
Should clarify that those png in one folder can only be removed if there is a png of the same name in another folder. Some png's like the ones in the SystemUi.apk and Framework-res.apk can only be re-sized to a point while others the xml does the re-sizing if needed.
Well you need to change the color of the text... I suggest decompiling the framework-res.apk so you can edit the text xmls. Most of the stuff you want to change is really just pngs, like what jerry, earthnfire, and I mentioned before.