Which mixture can create a light blue-green colour?

Correct answer: Blue-green and white

Blue-green is the base hue, and adding white produces a tint of that hue. Thus mixing blue-green with white creates light blue-green while preserving its blue-green identity. Red and white create pink or light red, orange and black create a darkened orange-brown effect, and yellow with violet tends toward a dull or neutral mixture. Therefore, option C is correct.