Color Coding Null Data Fields

It looks like the method is working fine and applying the background color command to the Item css field. But how does that translate to the specific field css? (in the case above actually turning "internal" red) If this is a simple question, could you please point me to some resources.

It looks like the method is working fine and applying the background color command to the Item css field. But how does that translate to the specific field css? (in the case above actually turning "internal" red) If this is a simple question, could you please point me to some resources.