Don,
You might get a more intelligent reply if you told us what year truck you are working on. That would help tremendously.
On both my '62 and '63 C10s, the high beam indicator was a standard clear bulb, but had a red lense on the cardboard tube that was between the front and rear of the speedometer and housed the bulb when it was installed. The wiring consists of a single light green wire and ground is provided by the speedometer housing. The high beam indicator is in the center of the speedometer, above the needle.
Speedo_HighBeamI hope this helps you.
