In Harmony, there is an advanced concept for painting your drawings called Line Art and Colour Art. Basically, an extra layer is added in your drawings so that you can fill the colour zones on a separate layer. The regular layer on which you are drawing is called Line Art and the extra layer under the Line Art is the Colour Art.
A shape drawn in Colour Art can only be morphed with another shape existing in the Colour Art.
A shape drawn in Line Art can only be morphed with another shape existing in the Line Art.
A shape created in Colour Art can never morph with a shape created in Line Art.