Some apps in iOS 7 have white text in top bar I am facing this issue with few apps, for example in this case with RedLaser. I am sure that this is not a problem with the app since the bar looks fine on other phones (i.e. text is written in black over a white background).

I have tried deleting the app and reinstalling it. I have also tried resetting the iPhone settings (iOS 7.0.3 on iPhone 5). But I am still facing this problem.

Is there some setting in the phones which forces the text to be white for some apps?
I don't think there is any way to change it in your iPhone. It is up to the programmer to set the colour of status bar that will be shown. What you can do is to write a review for the app, and it might get corrected in the next version of the app.