Possible Costumes, hair and make up.

Costumes;
Possible costume choices include;
Costumes which hide identity,
Boots, Long trench coats, hats, sunglasses and maybe Balaclava.
For victim,
Casual clothes but doesn't place him/her into a stereotype;
Hoodie, t-shirt, jeans, trainers. These clothes show a lack of identity for the victim showing it could be anyone.

Hair and make up;
Pale face make up for victim to add realism of the murder.
Dark make up for the 'shady fellow'.
Natural make up for the 'luring' female.
Messy hair for the male victim.
Natural hair for the female.
Tied up hair for the shady fellow.