common anode rgb with anode hooked to 5v and cathodes on teensy 3.6 i/o?

[mmalex]

i know the 3.6 isnt 5v tolerant, but if I wanted to drive a single common anode RGB LED with minimal part count whose forward voltage is very close to 3.3v (3.1v it seems from the data sheet), could I hook the common anode to 5v (Vin) and then the 3 cathodes (thru current limiting resistors) to digital output pins, even tho they will only go from 0-3.3v. my thinking is- the forward voltage on the red led is 1.8v, but the G/B is over 3.1v - feels a bit close to 3.3v? so I was thinking it might be ok if the anode was 5v, as the drop across the LED means that the pin would never see more than 5-1.8v which is under 3.3v. am I going mad?
should I just run it off 3.3v at the anode and be happy?
sorry for the dumb question.

 

[grease_lighting]

Going by the math you are correct. However there may be some current limit per group of pins that may become a fly in the ointment. Also if one of the LEDs gets accidently shorted Cathode to anode, you're out of luck. The best/safest way to drive discrete LEDs from a Teensy digital pin would be to use a (digital) transistor or MOSFET to drive the LED. That way when accidents happen, you will only have to replace a $0.20 transistor and not a $30.00 Teensy. There are also transistor arrays, quad, hex or octal buffers that have several drive channels in a single package which would help save space too.