The girl will be wearing casual clothes, which are mainly white, but with a bit of red on the clothes, to suggest danger. The girl should be wearing a hoodie, that covers her eyes and maybe the majority of her face. This will suggest that although she is "good" she has something to hide.
The boy will also be wearing casual clothes, which will be mainly black, grey and other drab colours, but maybe with some purple to suggest mystery. The casual clothes shouldn't conceal his face, to suggest that maybe he isn't "bad".