In my opinion it should be very easy to port the esp8266 NeoPixel driver (https://github.com/micropython/micropython/blob/ddb53c9458381f71d896ebba60234716f1b156d9/ports/esp8266/modules/neopixel.py and https://github.com/micropython/micropython/blob/0fff2e03fe07471997a6df6f92c6960cfd225dc0/ports/esp8266/espneopixel.c) to XBee 3, because there is no need for SPI, but only GPIO.