It shouldn't matter weather its IR or green or blue or red, the sensor is probably just an LDR ( Light dependant resistor ) which will sense any light . It would use a circuit like this :
( Note the LED would we swapped with A Not Gate, and Resisitor 2 and the LDR would also swap places ) This circuit detects low levels of light and turns the LED on when light level is low .
Diachi