No, it's doing it for e-mail and SMS too, actually. I use K-9 e-mail for all my e-mail accounts though. I also use Handcent for SMS.
I know all of this text was white with the standard SS 4.4/4.5 theme.
OH, now I get it,,,wish I had know that before wasting so much time...you have to modify Market apps yourself to get them to do white text with a black background in the Status/Notification, all of the Stock apps in my Theme will have white text in notifications (Market, Music, G-mail, Mesaging, etc)...for "non-stock" Market apps you are on your own with those, sorry.