Well the easy way I would think is to obtain a tach or other device with an RPM shift light and adapt that
Have you tried hooking up BOTH white and red to see what it looks like. If that is acceptable, you could then simply use the shift light to trigger the red
If you want to shut off the white, that would be a bit more complicated
One way to do that simply would be to use a little relay triggered by the tach light.
Frankly, you might "suggest" to the company that they build that in!!
