I went to the Microsoft store and they opened a new phone, installed the same apps and saw the same problem. Test it yourselves with the flixster app
You're right... I tested it with Flixster, and the background is messed up like this. Out of curiosity, I checked out Flixster on a few of my other phones (all W10M fast ring,) and it looks like it's a display resolution issue, likely something to do with the older WP8 apps on W10M.
On a 950 (1440p) the background is purple and interlaced-looking, then partially its normal, proper blue on the right-most pivot, the Favorites one. On a 1520 (1080p) it's purple and interlaced on every pivot, only showing the normal blue when transitioning between the Favorites pivot and main one. On both a 640 (720p) and 520 (480p) it's the proper blue everywhere, no purple interlaced seen.