There is an app called iFile. I believe it's a pay app. However, there very well may be free apps that let you navigate through your iPhone's file & folder system.
is just the path to go to to get to your icon cache. If you delete those, your white icon problem may go away. After I installed the theme I have installed, I had a couple of white icons. I used iFile to delete that cache, and the white icons changed to their themed icons.