Hi Royne and welcome!
That sounds like quite a find - good luck with the restoration! I have a couple of 4000's but am not sure what kind of grey/cream colour the cases are - I certainly don't know if there is a specific name for it. Try looking at some of the images of A4000's on this site in the Images section - that might help. Also, for parts, check out Amigakit.
Looking forward to seeing how you get on!
All the best
Retro :-)