How to change standard resources on phone/emulator

I'm a new in Android and Java and I have the following proble开发者_开发知识库m. I want to change standard resources, such as button background, programatically to allow applications using standard buttons be displayed with custom background. My problem is - how shall I identify the path for retrieval resources on phone or emulator? And if we have permissions to access to those resources?

The only way you can change "standard resources" for the entire device is to modify and install your own firmware.