I assume you have adjusted the screen brightness levels. Even though you are using the same wallpaper as on previous phones, I'm seeing a lot of complaints on here about the screen color saturation on the new phone. Perhaps try changing the wallpaper to something with more contrast to the pin pad. If you switch to a password, you get a text bubble to enter it. I think I saw someone mention that you can go into display settings and choose Vivid and then there's a slider for level of vividness. I could be hallucinating, though and I wouldn't know where to find the comment again even if I did see it.
