Should I take my iphone back?

I got the iPhone 5s a couple weeks ago. Something that has been bugging me is sometimes when I turn the screen off it flashes a dark blue screen for about a second. I know it doesn't sound like a big deal but it makes me wonder if more things are going to go wrong with this iphone. And plus it's really annoying. It's an expensive phone and everything should be working normally. I shouldn't see a blue screen flash when I turn the screen off. Would you take it back to apple if this happened to you? Or am I overreacting?

Hard to say what you are talking about, but I haven't turned my 5S off in a year, you never need to turn an iphone off, just flip the mute button in the corner at night

It might be a problem with the display. You should take it to the store and if they see that, they'll try to reset the phone and if it still does that, they'll replace the phone with a new one. So before taking it to the store, you should back up everything on iTunes and when you get the new phone, just restore. You can also back up on iCloud and your computer.