All themes work the same. Any new theme you create (by editing the .css file) would have the same problems, if any, as the built in themes. If you select the same theme for each layout the colors will be consistent. You would edit the .css file if you wanted a different theme than what is provided by filemaker.
Custom Theme Video
FMP12 Theme Engine Part 1
Overview Of themes In FileMaker Pro
What are the new features and functionality of themes in FileMaker Pro?
Answer ID: 10785Last Updated: Jul 17, 2012