Wiring up a tach?

You should have 4 wires 1 green 1 red 1 black and 1 white. The black goes to ground, the red goes to ign. on hot, the green goes to neg coil terminal and the white goes to lights best place to attach is at dimmer switch. Hope that helps.
what color is the hot coming off the ign? and whats the best way to splice these wires together in said placed?