I have the gasper ECU and the rpm sensor can be plugged in the both ways, the label shows the colors ok but it still can be done.
Another thing I thought about is, it is very easy on the gasper ECU to mix up the EGT and RPM positions on the ECU as one is above the other and depends on which way you look at the label. Same goes for the fuel and gas valve as I had these the wrong way around myself in the early days. Maybe the regal ecu is more clear.