Somewhere in CSS can indicate ...
/usr/share/themes/blanco/meegotouch/constants.ini
BACKGROUND_PORTRAIT = picture;
BACKGROUND_LANDSCAPE = picture-landscape;
BACKGROUND_INVERTED_PORTRAIT = picture;
BACKGROUND_INVERTED_LANDSCAPE = picture-landscape;
Pictures of picture and picture-landscape put in / usr / share / themes / blanco / meegotouch / images / backgrounds
But with the font color everything is much harder ... Simply put the finished theme with a black background.