Always a good idea. 
I wasn't suggesting they were RGBW in the OP. It was SteveMann who for whatever reason, interjected that. Merely commenting on the actual nature of the RGBW LEDs.
These clocked LEDs have no relation whatsoever to I²C (other than the synchronisation step), but I wonder why the libraries would have a problem with interrupts? Clearly the NeoPixel library must turn off interrupts for that sort (WS2812), but why would it not recognise that is not at all appropriate for the clocked LEDs?