You have two options really -
1. Advanced buttons allow anything to be the pressed & selected state including your own graphics. However these can be time consuming to do a large number of and also I believe they are not as optimal for performance (More of an issue if you are writing a UI for a legacy x50 panel or older iPad).
2. Create a new theme - You can download the CT_Neo theme from the Application market (you need the reasources and the theme export). Open it in Studio and save as a new theme - you can then do the file name swap in reasources to load your new files in place. This takes longer to do to change a few buttons but if you do a comprehensive job of modifiying the graphics you will have a reuseable theme. (In general the Studio theme editing is a bit wierd and not very well documented but if you are simply looking to colour swap or make mild modifications its easy enough)
