Changing field color based on a selection of another field.

I wanted to be able to select Critical or Gating on Urgency Level field and depending on what I selected, I want the "[Critical/Gating_Audit_OBC Descriptions]" field text to change color.

Case([Urgency Level],
"Critical", "<div style=\"color:black; background-color:Red;\">&[Critical/Gating_Audit_OBC Descriptions]&</div>", 
"Gating", "<div style=\"background-color:Yellow;\">&[Critical/Gating_Audit_OBC Descriptions]&</div>", "")