I prefer Wedgwood (one on the left). I think it will withstand use and abuse better. I’m afraid the darker blue will make the built in look cave-like, and will also show scuffs and dirt more. Which is why I hesitate to ever buy another black or very dark blue car. ;-)

What is the floor color? Both colors will look great. The navy would be would be more sophisticated and easier to design around, but it would show wear and tear more. The blue will be more fun, but could box you in when it comes to other decor.

I prefer the darker paint. If you are painting just he back wall the dark color will help the space recede visually making it feel larger.It will be easier to design around and provide contrast.

This is the tile we have (very light gray 12X24 Procelain)

I prefer the darker paint. I am partial to darker jewel tones. I just think it can make an otherwise ordinary area look more rich and less dull and utilitarian.