Is it possible to create (using grafting) a Lilac (Syringa vulgaris) which has different colors? One branch with white flowers, the other with lilac?
It would appear you can:
This page is specific for lilac trees and includes some grafting advice. In particular, quote:
The list of expert answers has a number of references to lilacs reverting to their rooting stock colour: (ie. multiple colours are possible on the same plant via grafting)