7. (4 points) In an opaque cloth bag, there are 10 chopsticks each of black, white, and yellow colors. The minimum number of chopsticks to be taken out to ensure that there is a pair of chopsticks of the same color is $\qquad$.
【Answer】Solution: Consider the three colors of chopsticks as three drawers, each for black, white, and yellow chopsticks. In the worst-case scenario, if you take 3 chopsticks, each of a different color, and place them in the three drawers, then by taking any additional 1 chopstick, one of the drawers will have 2 chopsticks. This results in one drawer having 2 chopsticks, and the other two drawers each having 1 chopstick, totaling $2+1+1=4$ chopsticks.

Therefore, the answer is: 4.