If a red-orange sample appears more yellow than expected after drying, how should the next mixture be corrected?

Correct answer: By slightly increasing the red

The governing concept is controlled colour adjustment based on the dried sample. Red-orange lies between red and yellow; if the result appears too yellow, the mixture must be shifted toward red. Therefore option A is correct: increase the red slightly, make another small test, and reassess after drying. More yellow would intensify the error, while blue or white would change other properties rather than provide the direct hue correction.