How can colour be corrected immediately if it goes outside the boundary?

Correct answer: Lift the excess colour with a clean, slightly damp brush

When a water-based colour spills beyond its boundary, a clean brush that is only slightly damp can lift the excess pigment while it is still wet. Blotting the brush first prevents added water from spreading the stain. Therefore option A is correct. Adding more colour enlarges the spill, folding can damage the paper, and a thick black line hides rather than corrects the mistake.