I guess you don't want anyone to know it's a SONY!
I wouldn't know how to do that, I think I read somewhere that some people got distracted by the sony logo on ereader and they were wondering what to do. Maybe one of those people will help you out. I don't know if black nail color paint would do it? Just like they have "white out" ..... I wonder if they have a bottle called "black out". I'm sure as marketing tactic , it could be kind of cool. Name is catchy!