That is a light added by a previous owner for something. Where the light is used to be a switch that would go either upwards, or downwards to activate the fuel gauges. They probably removed the switch when the gauges were changed since those are not the gauges that would have come with the boat. The STBD and the Port are in fact a remnant of the old fuel gauge switch.
Its funny to see what dealers and other owners have done, my spare switch is my bilge blower switch since my datamarine is located where the blower switch used to be (left of the helm wheel).
Tracing wires is your only option, it didn't come from Carver like that.