What was found
DFW, REPEAT ITEM, CREW REPORTED AFTER TAKEOFF RT LG HAD A RED GEAR LIGHT INDICATION. GEAR DOOR OPEN LIGHT WAS INITIALLY OFF BUT THEN CAME ON. TURNED ENG HYD PUMPS ON & BOTH LIGHTS WENT OUT. EMERGENCY DECLARED FLIGHT RETURNED TO DFW LANDED WITHOUT INCIDENT. ACFT REMOVED FROM SERVICE. REPLACED RT MLG LATCH CYLINDER & DOOR ACTUATOR. SYS GND CHECKED NORMAL, OPERATION CLOSED.