It's been a while since I've done anything really hands on. But I believe you can change
label.textColor = [UIColor blackColor]
If you want to make it black. You may want to change the shadowing as well (label.shadowColor) to something more appropriate if you'd like.
I don't have a theme that I can sample on, but if you can provide one, I can probably play around with it if you're unsure.