Don't ask where they came from but here is the color code you are looking for.
What Are These Colored Wires On My Tach For?
• Red = key on power supply
• Black = common chassis ground
• White = dash lighting power
• Green = tachometer signal for standard or electronic ignitions
• Yellow = used only on Internal Coil Magneto tachometers as the signal wire
• Twin Black = (looks like a lamp cord) is used on External Coil Magneto tachometers that use an inductive pick up (#5210)
• Gray = for tachometers that use a Hi/Lo shift light. When grounded, Lo shift light point is active. When ungrounded, Hi shift light point is active.
• Blue = used on Playback tachometers to start recording (see playback tachometer instructions)