There aren't
Only one is truly 'hot' - the Black/Blue
The reason the other (Purple/Black) 'appears' hot is because you are measuring the voltage while it is still attached to the horn; there is no current flowing through the horn unless the horn button is pressed so there is no voltage drop across the horn; if you disconnect the Purple/black from the horn and turn on ignition you will find there is NO voltage on the wire, but if you measure on that open terminal, you will see it there.