Ah, good old ocean grey... (or is it military grey?)
I wasn't that convinced when looking at your screenshot that the aspect ratio of the display is indeed 16:9. It's not square-on to the camera, but when I cropped out the display from your screenshot and measured its aspect ratio, it was 1.4:1, which is closer to 4:3 (1.33:1) than 16:9 (1.78:1).
As to the flatscreen element, I believe that the images on the mirror/display were in fact superimposed in post-production (or a reflective sheet was used instead when used as a mirror). If you've got episode 6 (me[sup]2[/sup]) to hand, have a look at when Lister's watching the video of Rimmer's death (09:15 to 09:30 in). The video image can be seen drifting down and across slightly, overlapping the display screen's border, and revealing the plain military grey paint behind. Or is it ocean grey paint?