What colour grout for black floor tiles

[joe90]

I am about to tile my sunspace floor in porcelain imitation riven slate tiles in black, some may remember I was slightly disappointed wth my kitchen floor with grey tiles and charcoal grout where the grout appears the same as the tiles. So the question is what colour grout would you use with these black tiles bearing in mind it will have plants, be the back door and we have a dog so white is definitely out.

[PeterW]

I’ve just used Bostick grey flex from Wickes with black limestone and it looks good.