Hate to say it: grout is the least of the issue. The tub shower did NOT need the "accent" at all. It's a totally different look/feel and makes little sense with the 2" hex. I'd stop right now, and do one or the other over, Floor or tub walls. ...............: ( So Sorry. Easiest would be floor, to a very simple light gray porcelain , A larger subway than your shower, a tone from the accent. Just looks quite disjointed, and style/scale/ incompatible. You'd prefer I lie, I am certain. But a course reversal would give you a better result.

Actually. that is a pretty bad placement of the accent tile, ( too high , needs more subway white above it when I blow up the pic. Shower do over, if you want a really good result. Aurrggh. AURRGGH. Aurrrgh. Stuff like this really makes me want to cry- I think shower do over. With apologies as well. Take a couple more pics of the tub area, especially near top. Even if fixed, the floor would be a do over , for me. Add tile to ceiling above the accent, rip the hex on the floor and re select. ......bummer.