How would you apply the tile on the stair treads? The rise needs to remain 100% consistent for every step and not sure this will happen with the tile added to the current treads.

the staircase in the picture is wood. stained or painted gray. I suggest you do the same thing.

you don't want tile on the stair treads. too difficult to edge out. (if you want to use the tile on the risers, you can do that, just paint the tread the gray color)