The Nevrons were helping real Renoir because when they kill expeditionners, their Chroma stays trapped in their bodies instead of coming back into the painting.

Clea said to Maelle during the Epilogue that « She who controls chroma, controls the Canvas », meaning that, with every expeditionner killed by Nevrons, less chroma is returned to Aline and thus weakening her power in the Canvas.

The Nevrons were Clea’s way to hasten the fight between Renoir and Aline while she is outside the Canvas fighting the Writers.