9. (3 points) Using red, yellow, blue, black, white, and green to paint each face of a cube (each face is painted with only one color), now four small cubes with exactly the same painting method are combined to form a rectangular prism, as shown in the figure. Try to answer: The opposite face of the red face on each small cube is $\qquad$ color, the opposite face of the yellow face is

color, and the opposite face of the black face is $\qquad$ color.
【Answer】Solution: From the above analysis, we know that,
red is opposite to green; yellow is opposite to blue; black is opposite to white. Therefore, the answers are: (1) green; (2) blue; (3) white.