It’s easier to do in Harmony Premium where you have a colour scale node.
In Animate you would need to duplicate the character’s face and place it just behind
the original face. The new face would be painted with the red face colours.
fade out the original face to reveal
the red face.
You would need to drop the face on a transparency node and keyframe the
transparency values to do it.
Alternately the red face could be in front transparent from the start and
only made visible for the time it is needed.