If a mixed colour becomes muddy, what is the best action?

Correct answer: Make a new mixture on a clean palette

The governing concept is clean colour mixing and avoidance of unnecessary pigment contamination. A muddy colour often results from overmixing or combining too many opposing pigments. Continuing to add colours, black or excessive water usually reduces clarity further. Therefore option D is best: start a fresh mixture on a clean palette, measure the needed colours carefully and mix only until the target hue is reached.