Are you referring to the contact list, or individual contact cards? The background when I open the Contacts app and look at the list, it is black text on white background. I do not see any place to adjust that. My contact cards are kind of a light blue background with white text. Other contact cards are ones the contact sent and/or shares with others. I'm still not finding a way on the contact card edit to change text color. Even the card I created for myself has that light blue background and the text is white, but the places where there are entries, i.e. phone, email, etc. have a darker background to make they stand out more. You would need to explain a little more where you are experiencing a problem.