This is a wonderful wallpaper called Paper Illusions. My bedroom had paneling and this covered the grooves. You tear it up, wet it and hang the piecing.
I adore it and have done my entire house with it (of different papers of course) The one room I have left is my sewing room, I'm starting it this week with a powder blue marble.
Cobalt blue is a color I have difficulty filming, is seems the camera wants to decide the shade but these 2 photos are pretty close...