Crossed posts. But more from the FCOM:
Landing Gear Configuration Warnings
Visual indications and aural warnings of landing gear position are provided by the
landing gear indicator lights and landing gear warning horn.
Visual Indications
The landing gear indication lights are activated by signals from each gear, the
LANDING GEAR lever, and the forward thrust lever position as follows:
Green light illuminated – landing gear is down and locked.
Red light illuminated –
• landing gear is in disagreement with LANDING GEAR lever position (in
transit or unsafe).
• landing gear is not down and locked--with either or both forward thrust
levers retarded to idle.
All lights extinguished – landing gear is up and locked with the LANDING GEAR
lever UP or OFF.
Found it here:
B737E Warning Systems