I hope you got a big discount for his mistake.

A strip of mosaic tile that coordinates with, but does not match, the floor tile? So it looks like an intentional accent.

Color matching custom made solid surface trim. It'll look like you planned it.

@joseph so like for countertops? Any picture or link to product you could provide?

@sofia thanks, forgot to put we thought of that as well but there’s no other place in the bathroom to incorporate so it dies look intentional. Appreciate the thought!

@cpartist no discount and we paid a premium for timeliness. Also a family member of a good friend so we decided to save the relationship rather than squabble over the $’s

Solid surface as Joe says, same color as tub, laid flat flush with tile so your eye doesn't notice so much.

I know nothing about tiles (I leave it all to installer), but isn't there something called a flat liner? It wouldn't have to be an exact match to the tile you have...something like this in a marble...

Sorry, that's my rescue...hit the wrong photo.

If it would cover the error, this would look okay with the white of the tub and the dark of the floor.

I was thinking along the same lines as Joseph and Judianna - if you can find a similar texture to either the tub or the floor tile, and a compatible shade of gray (without being a match) or matching white, with a similar linear shape that could work.

Look for bullnose, cove, chair rail tiles

PVC Trim Board, ripped down to the width you need. Same concept as solid surface, but DIY-able. Comes in 5/8" and 3/4" thickness.