The sky will flicker various shades of blue while running. I've noticed this while going across open fields, but it is quite possible that it is a more general graphical bug. I have bloom completely turned off as well as various forms of enhancements (see screenshots of settings).

The first screenshot is just one location where I observed it. It has occurred a lot, but it is a bit subtle. {F28642} {F28643} {F28644} {F28645} {F28646}