Had to look up justina blakeney, and found this pic supposedly from her book, perhaps a blue like this would contrast nicely with the dark grey, go well with the bright colored interior, and still be toned down enough from bright red or orange....

Great job of narrowing down the colors! Chelsea Gray HC-168 is a great neutral gray that’s popular for exteriors. Cinder AF-705 takes on a purplish hue in comparison to Chelsea Gray however can work with your navy door. Geddy Gray CW-720 is very similar to Chelsea Gray which also makes it a great, and a safe choice. Be sure to view it next to your door to ensure there’s enough contrast between the gray and the blue. Good luck!

I put it in five years ago and it's been great. It is grouted. The only damage reviews I saw were in kitchens where people were pushing chairs back and forth. That's not an issue in bathrooms. I haven't found it hard to clean but I don't wear shoes in there. I mop it with hot water now and then. Usually I just go over it with a damp terry cloth rag. I'm using the same tile in my master bath. This is one of my leftover tiles.

You can buy flex trim in several profiles, you'll just have to make sure that the flex trim matches a profile that is installed on the straight walls. You could consider holding the flex trim up from the floor so that the tile slides in underneath. Baseboard is usually held up a small distance to accomodate tile or carpet, this depends on the height you need for the entire area.