What kind of colour can generally form by mixing blue and orange?

Correct answer: Muted brown or grey

The relevant principle is complementary colour mixing. Blue and orange occupy opposite positions on the traditional colour wheel, so they are complementary. In paint, their pigments partially cancel one another and reduce saturation, usually producing a neutralised muted brown, grey, or brown-grey colour. Therefore option C is correct. Bright green, pure red, and light yellow are not the normal direct result of this complementary mixture.