Why may an orange object appear relatively muted under blue light?

Correct answer: Blue is complementary to orange

The governing concept is complementary colour interaction under coloured illumination. Orange and blue lie opposite one another on a traditional colour wheel. Blue light does not supply the warm wavelengths that an orange surface reflects most strongly, so the orange can lose apparent chroma and look duller or more muted. This does not mean orange becomes a cool colour, all colour disappears, or its value must always become darker. Therefore, option A is correct.