Then, as if sensing my presence, the girl turned around. She looked young. Probably sixteen or seventeen. She had long black hair, crimson red lips, and a skin so pale it made me wonder whether she had blood at all. But what struck me the most were her eyes. Even though there was nothing unusual in them, they made her face look lifeless, completely devoid of expression. It felt strange. Like staring at an empty canvas.
In the last part I'm telling the reader the girl's eyes make her face look lifeless. I didn't actually describe them (e.g. they were black, white, etc.) But, I don't know, I think I'm also showing the reader how her face looks by stating what it's lacking?