I can't see any issue there at all personally, it looks fine to me, but dials from this era can develop issues if there has been a slight water ingress issue at some point ie fogging or similar. SL lume only really degrades due to outside influnences, if left alone it is very stable indeed. The lume backing as you call it is just a white paint plot, the lume is just the green stripe and that looks pristine, it probably looked exactly like that on day one.
I thought that model had gone before the SL lume came along in 1997 but I could be mistaken as I am not basing it on anything concrete. Is that actually a 2532.80 or is it another model with a dial or bezel swap? That configuration certainly didn't make it into the 2000s. It was replaced by the 2255.80 electric blue model I think.