Answer
When a red card is illuminated by red light, the red card still appears red.
When a red card is illuminated by blue light, the red card appears black.
Work Step by Step
A red card reflects red light and absorbs other colors of light.
When a red card is illuminated by red light, the red light is reflected. Therefore, the red card still appears red.
When a red card is illuminated by blue light, the blue light is absorbed, and no light is reflected. Therefore, the red card appears black.
