Most electronic speedos use 4 or 5 wires, positive and ground, two sensor wires and often an extra wire for use when two speed axles are used.
I'd be willing to bet the two blue with red tracer are the sensor wire and the extra white would get power from a two speed axle switch if used.
Sensors are not generally polarity sensitive (neither lead is grounded) so it doesn't matter which way you wire them to the sensor leads.
Done a bunch of trucks and they all seam that way. Converted my Marmon to electronic and added 2 spd axles and that was how it was done.