12v DC motor active indicator
Assuming the motors are on the same power supply and not on separate power switches, LEDs in parallel will only tell you the power supply is active.
You need to detect some current flow (motor active) but not too much current flow (motor stalled or bogged down) - and you want to do it without losing very much voltage in the detector ( 2V for a LED would only leave 10V for the motor ... unacceptable!)
Here's a sketch of a solution, losing about 1V in normal operation. If even that's too much, you'll need more sensitive amplifiers (probably opamps) to detect smaller voltages across lower resistance shunts.



simulate this circuit &ndash; Schematic created using CircuitLab
When the voltage across R1 reaches about 0.6V (1.5A) Q1 turns on, and D1 lights.
When the voltage across R1 reaches 4* 0.6V (set by voltage divider R3,R4) Q2 turns on, and the red light illuminates. Note the lower forward voltage of D2 allows it to steal the current from R2, so D1 goes dark, so the light turns red indicating a stalled or overloaded motor.
(D1 and D2 are available in a single package with a common anode)
If you don't want overcurrent indication, omit D2,Q2,R3,R4.
Ad if 1V drop is still too much, reduce R1, and insert a rail to rail opamp with a gain about 4, between R1 and Q1base/R3.