Hi,
Have you checked this documentation?
https://docs.moodle.org/dev/Moodle_Mobile_Themes#Styling_specific_pages
http://www.slideshare.net/juanleyva/creating-moodle-mobile-remote-themes
First link is the general documentation for developers
Second link is a Moodle Moot slide regarding Themes.
Regards,
Berta