Let's say you're writing the story from Della's point of view. You can say, "Della looked up into Rodney's adoring face," but you can't say, "Della raised her incredibly beautiful violet eyes to Rodney's adoring face."
Why not? Because although Della may be aware she's incredibly beautiful and has violet eyes, that's not what Della sees when she looks up. That's what Rodney sees. And Della is the person whose mind you're in.
Only Della's perceptions are perceptible. Rodney's aren't. And if Della really is thinking about the color of her own eyes, instead of how adorably adoring Rodney looks, you have to explain why: "She raised her eyes, knowing the effect their violet beauty would have on him."
If this still seems mysterious, consider that the limited third person is very like the first person in some ways; and you know that when you write as "I" you can tell only what "I" see and know. - "I raised my incredibly beautiful violet eyes to Rodney's adoring face." I'm sure you see that you wouldn't write that.
Ursula K. Le Guin