Yes, they are 3mm LEDs.  The resistors on the PCB are setup for typical blue LEDs.  I have installed white LEDs that have a slightly lower Vf with some success.  I ended up adding a parallel resistor for the Nav key indicators, since there are 4 of them and they ended up dimmer than I liked.  If you go with another color, you may have to tweak the chip resistors accordingly.  There are 3 of them, IIRC.  That said, Vortex is not driving the stock blue LEDs at full power, so they may work OK for other LEDs with lower Vf for a given current.