First off, I love Benedict Cumberbatch, so of course I am going to love this, but there are other reasons too!
Your choice of color is excellent! It was a great idea to chose the blue for his suit coat because it brings out the color of his eyes.
I like your drawing style, too. The fuzzy softness of it sort of reminds me of pastels or chalk, but it keeps the tones and meticulousness of colors pencils. I like that.
Also, this is a fantastic likeness. It looks exactly like him! You captured his pose, eyes and eye color, face shape, physical features, and even his skin tone with almost perfection! His eyes and mouth may be the best captured I have ever seen.