On Jun 30, 1:58*pm, Kevin wrote:
There's large gaps behind the black granite upstands where the walls
aren't straight.
Ideal solution is to reskim the wall to level it off, but this isn't
going to happen. *We've decided best compromise is to use some black
filler, but I'm not sure if black caulk exists and I'm a little wary
of using silicone.

My mother's kitchen has black upstands and they have some from of
black sealer around them. Dunno whether it's caulk or silicone -
possibly the latter as ISTR it looks shinier than caulk.

Why are you wary of silicone? Could you perhaps paint the caulk black?