diff --git a/src/pan3d/widgets/color_by.py b/src/pan3d/widgets/color_by.py
index b45a4f2..0f7e9cb 100644
--- a/src/pan3d/widgets/color_by.py
+++ b/src/pan3d/widgets/color_by.py
@@ -412,3 +412,4 @@ def configure_mapper(self, mapper):
         mapper.SelectColorArray(self.color_by)
         mapper.SetScalarRange(self.color_min, self.color_max)
         mapper.SetScalarVisibility(1)
+        mapper.SetColorModeToMapScalars()  # Critical fix: Force use of lookup table