I would replace the brick coping with a natural stone with pieces a minimum of 30" long. Lose the boulders.

I see the patio is natural stone. Use natural stone again, but opt for larger pieces. The numerous joints make it look too busy.

Replace the tile with glass tile.

If you choose natural stone on the raised wall areas, make sure the stone runs below the water line. I see a lot of pools where the stone runs down on top of the perimeter tile. To me, it looks really cheesy.

I noticed the spa's bench had tiles along the edge. When we put tiles along the edge, they are generally 14"-16" apart set in a diamond configuration. Right now, your spa looks like a public spa. Sorry.

We set the tiles the same way on step edges and benches as well.

Lose all the brick on the steps and use the same material for the pool coping on the step treads. One piece treads-no joints. Only at the ends.

The interior finish can be in the gray family of colors. It's best to choose several tile and plaster finishes, set them outside next to each other to see how they look in the natural light.

Plaster colors change when wet, under water and at different depths at different times of the day. See how your coping material ties in also with other materials.

Look at finished pools by your contractor to see them in real time.