My experience is with a TR4 but FWIW -- the exterior was a flat gray, I would call it almost a dark grey. I honestly don't recall what the inside was like.
I have seen some variations in what is supplied as repros but the one I got from Moss was very close to the shabby original it replaced. My only objection to their part was that they slapped a sticky bar-code label right on the top -- very tricky to remove and not damage the soft fiberboard.
<span style="font-style: italic">Okay, I peeked inside the one I have on the TR4 -- hard to see of course, but the inside lookd just like the outside on the Moss version. A pebble-grain inside seems odd yet sounds familiar (like I have seen that part on someone elses TR). Perhaps a finish on the inside adds water resistance.</span>