If it was a miscommunication you might talk to the builder so the onus is not on you 100%. Big difference in white which you wanted and dark gray which was used. The builder should remedy this unless I'm missing something here...

What colour is the tile? Pics?

It's quite possible to remove the grout without damaging the tile, if the contractor is careful. Here's one set of instructions: https://www.thespruce.com/remove-tile-grout-in-a-few-simple-steps-1822630 Of course, a hexagonal tile would be a whole lot more difficult to do, since you don't have long straight lines.

There is stuff called Grout Renew which could be used, though I really think it wouldn't be as good as redoing the grout in the correct colour. BTW - you might want to think about going with white. It is hard to keep it looking flawless. We went with a pale grey in our white-tiled showers. Looks great.

Thank you Porter and Paddy. The builder is my husband and he has been busting his tail so telling him to fix it is not in our best interest :)! After researching several articles removing the grout would be the best thing. In my dream world was hoping there was a quick easy fix!