By default, all operations on the NeoPixels are immediately transferred to the lights. This works great to get started and for a small number of pixels. However, for large number of lights and for precise control of the timings, you might want to decide when to send the updates to the hardware.
To turn on buffering, call setBuffered.
Once buffering is on, you need to call show to send the color updates into the NeoPixels.
... some operations on the colors