It is lucky that you have a soak tub, my bath room is not wide enough to build one. I think the deep color decorated the bathroom would be good, because the white color will make the whole room dirty once there are only several hairs. What about the gray?

I like dark floors in a bathroom, they create a great visual anchor to build upon.

I have brazilian cherry (real wood) in my master bath, with teak countertops, teak tub deck, teak window sill, etc. The horizontal surfaces are teak. So I like dark materials and "real" wood.

Teak would be fine on your floor, but be careful with the color it can cast. In its natural tones, teak can be light reddish-brown to dark brown, or places in between. It can be stained if you choose.

So the floor, yes, teak, or a wood-look tile, all that can work. If you go tile, have the grout slightly darker to darker than the tile itself. Just an opinion.

Have your eyes open when considering a dark vanity on a dark floor. Depending on the "rest of the room", the dark-on-dark can sometimes create a bit of a black hole effect. It can indeed look wonderful...or it can look heavy. It can depend on not just the amount of dark versus white, but how it presents itself to you when you walk into the room. Right in front? Off to the side?

Pure white fixtures and pure white tile with a dark vanity and dark floors can sometimes be a bit stark. Compare that with a slightly off-white, or a slightly cream- or ivory-colored tile and fixtures. Just a tad away from "white" white. Again, just an opinion.

Regarding the "blue insert" on a white ceramic tiled floor. The "insert" can be subtle or it can be prominent. Blue can look great or it can look horrible. But it is a color. And when you introduce a color like blue tile into your tiled floor, which is essentially a permanent material in a bathroom, you've sort of defined the color direction that you are going in that room.

If blue is your color, then there you go. But if your floor (tile or wood) is by itself a dark neutral color, then you can change the color scheme of your bath as your mood changes with colored floor mats, towels, and with a little more effort, changing the window shades or the color of the wall paint. Feel like blue? Blue towels, etc.

It can sometimes help to go on a photo site like Houzz and do various searches. You'll eventually discover a trend within the photos that you like, it's an easy way to help you nail down your style. What you like. What you don't like.

Good luck!