Changing texture main color causes lighting to be ignored?

The dice at the bottom were dragged into the scene manually, the dice at the top were spawned and re-tinted via code (to the same values that the prefab has by default).

Why is lightning being ignored?

For reference, I'm using default diffuse shaders.

Code:

 //for ease of reading, the prefab switch statement has been omitted
 inst = Instantiate(colorizedPrefabd10,pos,Quaternion.identity) as GameObject;

 Renderer[] renders = inst.GetComponentsInChildren<Renderer>();
 int i = 0;
 foreach(Renderer r in renders) {
     if(Size >= 8) {
         switch(i) {
             case 0:
                 r.material.color = numberColor;//numbers (transparent diffuse)
                 break;
             case 1:
                 r.material.color = overlayColor;//overlay (transparent diffuse)
                 break;
             case 2:
                 r.material.color = baseColor;//underlay (diffuse)
                 break;
             default:
                 break;
         }
     }
 }
 //after this it's the d4 and d6 else-blocks, then adding random force and torque.

If I comment out the r.material.color lines, the lighting remains normal, but I don't get the user-defined colors.