Which colour forms when a violet mixture contains more red?

Correct answer: Red-violet

The governing concept is directional change on the colour wheel. Violet is formed from red and blue; when red is present in a greater proportion, the mixture shifts toward red and becomes red-violet. Thus option D is correct. Blue-violet would result from stronger blue influence, while yellow-green and red-orange are not the immediate hue direction of a violet mixture with extra red.