Two identical blocks have identical face configurations. Each block has 6 faces. A black face is opposite a white face. There is a grey face. How many faces of each color can there be?

Step 1: Determine the face configuration of each identical block.
Each block has 6 faces. We are given two conditions:

1. "A black face is opposite a white face." This implies that for every black face, its opposite face is white, and vice versa. Therefore, the number of black faces ($N_B$) must equal the number of white faces ($N_W$).
2. "There is a grey face." This means the number of grey faces ($N_G$) must be at least 1 ($N_G \ge 1$).

The total number of faces is 6. So, $N_B + N_W + N_G = 6$.
Since $N_B = N_W$, we have $2