I love the green and white tiles, keep them, theyre what you wanted.  If swapping the larger 'white' tiles is not an option then live with them.  Grout them all the same for simplicity (probably white).  When the room is complete and dressed it will look different.  We had similar, used a bathroom satin version of a white paint we have always loved in matt emulsion.  In our bathroom light it looks slightly green and therefore made out white tiles look slightly pink, we were gutted! Couldn't stomach repainting straight away as the bathroom and floor had been fitted.  We have lived with it a few months now.  While I'm still not keen on the 'satin' finish of the bathroom paint (we didn't know you could get matt bathroom paint!) The colour differences really don't seem as prominent as they once were.  Try not to worry.  We said 'if it still bothers us in a year'.

Thanks for the feedback so far. I went a bit overboard with a few of the 3D renderings just for fun. Unfortunately they dont have tile from the same manufacturer, however they have a plain white terrazzo with small specks. I am sure that Teracotta towels, bathmat and maybe a terrazzo soap dispencer would look great as well. Bellow a 3D rendering of @colourhappy's idea. I liked the white terrazzo, so I found from the same manufacturer the grey which I thought would be nice for the floor. Further on I tried to combine plain colours as @Sonia, I reckon I would need to tone down a bit the colour on the walls. I went a little bit crazy here. 😅 Black wall tile was just an experiement. 😆 Thanks for your ideas so far. If anyone else have some, I would be more then happy to make a 3D rendering. I guess we will make a vote for the best? Any thoughts with the above?

I like the blue - and for me, I think I would prefer to replace the border tiles with the same. However I appreciate it can be really tricky to find the exact tile! As an latter native I would consider maybe using a wood effect slatted style tile like these - and I would also get the tiler to tile the bath panel and the boxing in around the sink.

Ultimately it depends on your budget. If there is nothing wrong with the white tiles, you can certainly leave them, but if you’re replacing pretty much everything else, you might regret not replacing them at the same time. Browsing photos of Houzz, having the shower end of a bath as a feature wall seems to be old fashioned now. It would be more modern to have all three walls the same tile. I would also take the opportunity to make a niche (if there is space behind a wall) so that you can put shampoo bottles somewhere and not around the edge of the bath. It was the best thing I did for my bathroom! You should also be prepared to replace the floor. It’s hard to imagine that the floor won’t be damaged when the sink comes out or that there won’t be gaps if the replacement is a different shape or size.