Depends what you mean by mix. If you mean some fancy shizzle then I'd doubt it if it's just a friend's party or something like that.
If you mean something like Vodka and coke, then there's not really a set rule for it. But generally, dark alcohol goes with dark drinks and white goes with any. That's not to say you couldn't mix something like aged whiskey with lemonade though.
White alcohol is clear stuff like white rum, most Vodkas, Silver Tequila (Blanco or Plata),ect....
Dark alcohol, in this context anyway, basically includes anything with colour. So aged whisk(e)y, aged rum, aged tequila (Reposado, Añejo. Extra Añejo, Reserva de Casa and Reserva de la Familia), ect...