What effect is produced if red-orange contains more red?

Correct answer: The colour will lean toward red

The governing concept is colour proportion in a mixture. Red-orange lies between red and orange, so increasing the amount of red changes the balance toward the red side. Hence option B is correct. Increasing orange would move the mixture toward orange, while green or blue would introduce different hues rather than simply strengthen the existing red-orange bias. The result is a redder, warmer version of the original tertiary colour.