My font would be white.. and most of the images are dark.. but its a good point with the mobile devices..
the font shouldnt be "opaced" the font should have a opacity of 0%
It will not generally be functional. Even if the font is white on dark photos, it looks cluttered and is therefore not a feature of X3. With knowledge of CSS, it is technically possible to code your own styles, but I wouldn't recommend it without proper planning.