is
Whether color has been assigned after this paint was constructed, i.e. by the host app rather than by the built-in layer configuration.
MVT features frequently carry their own COLOR property, and the fill renderer prefers it so that products like alerts keep their per-product colors. That preference has to yield when an app has explicitly asked for a different color, otherwise the assignment silently does nothing — see VectorPolygonFillTriangulator.parseFillColor.
Only a post-construction assignment counts. Built-in configurations set their color through the constructor, so their rendering is unaffected.