While I don't grow grafted plants, it would appear it's a goner.

These are seedlings of the same species but these have chlorophyl and grow on their own roots. They flower all summer long and into the fall/winter sometimes. They are normally more green but with all the sun they turn this red color. Comes the winter they tend to return to their green bodies.

The whole thing -- both the stock plant (formerly green part) and the graft -- are compost at this point. Nothing to save or salvage.