There are lots of reasons for Rose's favorite color to be silver.
Silver is the color of Unicron blood. Silver is the color of her favorite ring her Aunt Ginny gave her when she was 7. Silver symbolizes security, reliability, and intelligence. But those aren't the reason for her love of that color.
She loves the color silver because it's the color of his eyes. When she looks into his eyes she gets a feeling of security, like she can't be safer anywhere else but with him.
She loves the color silver because it's the color of the shirt he wore when she finally got the git to kiss her. They were watching the stars one night alone in the Ravenclaw common room. "Beautiful" he had said. "I know, stars look lovely this time of night." She told him. "I wasn't talking about the stars." He said to her. He leaned in and kissed her in the Ravenclaw common room, with the stars shining in the background nobody there to interupt the moment.
She loves the color silver because it reminds her of him.
Sorry for the short chapter. And how I haven't uploaded lately... School started and I'm LOADED with work to bring home! SO SORRY! Please review! It doesn't take very long!