- you can measure anything (apart from white LEDs in diode mode as 3.1V is max)
3.1V is enough to light a white LED.
Let me know, when you will succeed in doing so with a Fluke 289:

Cheers! 
DMMs can't do everything unassisted.
I had a bunch of LEDs to test with the Fluke 77.
For the ones it couldn't turn on, I just grabbed a half dead 9v battery, an appropriate series resistor from the junk box, & read the volts across the LED when it was lit,
Total cost of the "LED tester"------- zilch.