A compound absorbs light in the wavelength region 490-500 ~nm . Its complementary colour is

Step-by-step solution

When a compound absorbs a certain wavelength (i.e., 490 ~nm -500 ~nm ) from the visible light which corresponds to the blue-green light in the visible spectrum, the colour or light transmitted by it does not contain the colour of absorbed radiation and thus shows the complementary colour, i.e., red.