Which correction is suitable if blue-green appears more blue than expected?

Correct answer: Add a little green

The governing concept is restoring the balance between the named components of a tertiary colour. Blue-green contains blue and green. If blue is too dominant, adding a small amount of green increases the weaker component and brings the mixture toward the intended blue-green. Red or orange may neutralise or muddy the hue, while black mainly reduces lightness and does not correct the component balance directly.