Which two colours remain if yellow is missing from the primary-colour group?

Correct answer: Red and Blue

Start with the traditional primary-colour list: red, yellow, and blue. Removing yellow leaves red and blue, so option C is correct. Green is not a remaining primary colour because it is made by mixing yellow with blue. Orange is a secondary colour made from red and yellow, while black and white are not the two remaining members of this primary-colour set.