How to set colors fo Polydata for a custom reader?

I am implementing a custom reader. The reader is derived from vtkAbstractPolyDataReader. When I implement the RequestData function, I specify the points and polys, and I can get the correct geometric. For now, I want set the colors for different part of polys, and I set scalars for different polydata. However, when I load the model, I can’t get the correct color. The problem I found is that, the model use the magnitude of the specific colors. And how to set colors for different polydata in a right way?

The code I used in the custom reader (derived from vtkAbstractPolyDataReader)

vtkPolyData *ply = vtkPolyData::New();
ply->SetPoints(DS->GetOutput()->GetPoints());//set the points
ply->SetPolys(DS->GetOutput()->GetPolys());//set the polys
ply->GetPointData()->SetScalars(colors);//set the scalar colors [r,g,b]

You should uncheck the Map Scalars property in the Display section of the property panel.

Thanks a lot! I can get the correct color now.