Which tertiary colour may generally have a dark value because of blue and violet?

Correct answer: Blue-violet

The governing concept is colour value, not hue: value describes how light or dark a colour appears. Blue and violet are commonly perceived as lower-luminosity hues, so blue-violet can generally produce a darker-looking tertiary colour. Yellow-green, yellow-orange and red-orange contain stronger yellow or orange influence and often appear lighter. Pigment strength can change the result, but option C is the intended answer.