Whatever animal you hit with your car! Sporran doesn't have match nor compliment your kilt. Choose your favourite (or least favourite animal). Hose and flashes should compliment your kilt, perhaps even shirt or tie. Your leathers should match (shoes and belt) and the general "rule" of thumb there is black for formal, brown for daywear. Sporran can speak for it's self. Admittedly for my Canadian tartans I did choose beaver but if you're still stuck on it I say - fox (just because I like fox).