Set neopixel LEDs to a single colour using an adafruit feather huzzah

neopixel.ino

#include <Adafruit_NeoPixel.h>  // Include the Neopixel library
#ifdef __AVR__
#endif

// Which pin on the Arduino is connected to the NeoPixels?
#define PIN 4

// How many NeoPixels are attached to the Arduino?
#define NUMPIXELS 256 // Popular NeoPixel ring size

// Set up the NeoPixel library - tell it how many pixels,
// and which pin to use to send signals.
Adafruit_NeoPixel pixels(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  pixels.begin(); // INITIALIZE NeoPixel strip object
}

void loop() {
  // The first NeoPixel in a strand is #0, second is 1, all the way up
  // to the count of pixels minus one.
  for(int i=0; i<NUMPIXELS; i++) { // For each pixel...

    // pixels.Color() takes RGB values, from 0,0,0 up to 255,255,255
    // Here we're using red
    pixels.setPixelColor(i, pixels.Color(255, 0, 0));

    pixels.show();   // Send the updated pixel colors to the hardware.
  }
}