Transfer vertex color from a sphere to a tree model ?

Looking it this http://wiki.polycount.com/wiki/Foliage_Vertex_Color I wonder if instead of manually painting vertex color, I could just paint gradient vertex color on a sphere (that would encompass the tree) and then transfer vertex color from the sphere to the tree model (leaves/branches) automatically (and without any occlusions, so that vertex color could be transferred to every leaf properly).

How do I go about that ?

Thanks

Test out https://www.blender.org/manual/fr/modeling/modifiers/modify/data_transfer.html