Clean The Leather 

Use a silacone based leather cleaner for the leather leashes.  They make the leather waterproof, they keep the BLING in the Metallics &  the reds will not bleed when treated with these.  They can be found on, very reasonably priced.  Don't let your leashes get grungy,  or your dogs pink, use either lexol or search Amazon for leather cleaner and choose one that is clear, and the leather will look and feel better.