It can be hard to tell as a teen sometimes, but that hair color is definitely a mutation!
The Sims 3 genetic system isn't always the best, in my legacy I have Agnes and Tragic Clown have a baby (both of them are blond, Agnes has grey eyes and Tragic has blue) and I ended up with kids with townie-brown hair, red hair, and one even had orange eyes! Though all of them kept their features of their parents.
Honestly I feel that the lips look like Agnes (from this angle it's hard to tell), the eyes are all Chris and the nose is... I want to say Agnes but I couldn't be for sure!
The hair color though could be any variable (like I said I got a lot of different colors out of two blond haired sims).