Not a teacher
It's Bechstein model 8, am I right?
I don't know if it's correct, but the similar color of this piano are:
Beaver - Beaver is a medium, grayish brown with a cool undertone. It is similar to, but cooler in tone than taupe.
Bistre - Bistre is a very dark, semi cool shade of brown with similarities to dark brown and coffee, though darker than both of these shades.
I know you have something about this.