title_body: Is it possible to set font-color to the background-color
upvoted_answer: Let's analyze this question a little bit. 
  
  The 7; is it a background image or using some advanced css trick like this? https://stackoverflow.com/questions/15986216/how-can-i-add-a-large-faded-text-background-via-css
  
  I haven't studied the issue in depth, but ebook reading systems generally don't support background images for pages. They generally are behind the curve of css which is supported in web browsers today.  Maybe in the next generation of e-readers (5-10 years from now), this will become possible.  
  
  If you used a Fixed Layout Book format (on kindle or Apple), maybe you might achieve this effect, but doing so would use a fixed display size  and generally disable user controls. 
  
  You're asking for the moon, bro....