Hello allyallyally3, I think it depends how much contrast you want to show.. I don't think it will make anything look closer but the darker the more pronounced the aesthetic.. I quite like the dark and I think it looks really stylish.. (don't take notice that they are kitchen image- just to show the grout and how light or dark can look quite different.. Either way I think it's really nice! : ))

I think you might be right about grey and white overkill. It's a fashionable colour scheme at the moment, but it is rather cold, and could get dated very quickly if its not appropriate for the house. It looks like you're one of a pair of semis? It is usually best in this case to consider the overall effect of both houses. If you transform yours, and theirs is different, it can end up looking wrong. Is the render for insulation, or just aesthetics? A photo of the existing, including your neighbours would help.

Our advice in a small space/ bathroom would be to go with white as it creates an homogenous surface. Use anti mould grouts to assist the cleaning and maintenance. A light grey grout if grey at all, will make a white tiles wall seem very busy and smaller Black grout is very stark and unforgiving so I would not suggest one ventures into the darker range of greys, even in larger spaces.

I’d say white for the walls but definitely grey for the floor. Contrast can be achieved with towels and green leafy plants.