To further elaborate:The pink to coil. Orange to keyed hot.
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I'm squinting at a poorly printed wiring diagram that doesn't list the colors and also assuming that your bike's wiring is stock, so take the following for what it's worth. Follow the wires from the neutral/oil pressure/high beam idiot lights back to the first connector they plug into. Look for an unused connector hole on one end of that connector that has a pink wire on the opposite side running back into the wiring loom. That pink wire should go to the trigger on the coil, and you would connect the pink wire from your tach into the unused hole that meets up with it.
The "proper" orange wire location is more difficult to determine from my sh!tty wiring diagram. The speedometer should have an orange wire running to a connector. Follow it and see if there is an unused hole in the connector that would connect with orange on the opposite side. Note that some connectors are bridged, meaning that there is a metal connector inside the plastic wiring connector that connects one wire to one or more adjacent connectors, so you may need to examine both sides of the connector to be sure. If you find a vacant connector hole fed by orange on the opposite side I believe that is the one you want. As Alan mentioned orange is +12DC that is switched by the ignition key switch, so you could check it with a meter or test light to be sure. As you've already determined the black wire goes to ground.