If you place every object created with the Smart Fill tool in CorelDRAW on a separate layer, you can export your ready-to-color drawing to the Corel PHOTO-PAINT (CPT) file format  (with the Maintain layers check box enabled). When you open this file in Corel PHOTO-PAINT, you can color each object separately, without affecting other objects, by clicking the Lock Transparency button in the Objects docker.

Provided by Maurice Beumers, CorelDRAW  Master, Graphic Designer and Illustrator