Why is the cup tester's cup spoon either gold or silver? Cup spoon is also fastidious?

For the exchange of professional baristas, please follow the coffee workshop (Wechat official account cafe_style) nearby cup tester exam. After greeting the last guests who were left alone, I set up a bar and listed 6 groups of 5 bowls of bearer coffee for colleagues preparing for the exam. In the pocket is a small bag of specially prepared defective beans. Secretly put it into some bowls later, hoping they can confirm it.