Here is what the manual says about the red LED.
The PTO red LED (C) indicates that there is power to the PTO relay (D) coil through either of the following circuits:
• Key switch on, operator on seat, park brake disengaged, and PTO turned off (PTO pre- operation circuit).
• Key switch on, operator on seat, PTO turned on, park brake disengaged, and ignition relay engaged (PTO operation circuit).
When diagnosing a problem using the LEDs, and the LEDs are off, check that part of the circuit before the control/fuse module LEDs (neutral start or PTO pre- operation circuit). When the LEDs are on, check that part of the circuit after the control/fuse module LEDs. Tests for voltage or ground will be at the control connector (I) or the power connector (J) of the control/ fuse module and not on the printed circuit board paths.
The ignition relay (B), PTO relay (D), start relay (E), fuse terminals (H), key switch (K), ignition LED (A), and PTO LED (C) are mounted on a printed circuit board. The components are solid state and are not serviced separately except for the 15 amp fuses.