#include <Adafruit_NeoPixel.h>
int PIN = 12;
int N_LEDS = 16;
Adafruit_NeoPixel ring = Adafruit_NeoPixel(N_LEDS, PIN);

void setup() {
  // put your setup code here, to run once:
  ring.begin();
}

void loop() {
  // put your main code here, to run repeatedly:
  for(int i=0; i<N_LEDS; i++)
  { 
    ring.setPixelColor(i, ring.Color(0, 0, 255));
    ring.show();
    delay(500);
    if (i<8)
    {
      ring.setPixelColor(i, ring.Color(255, 0, 0));
      ring.show();
      delay(500);
    }
    else
    {
      ring.setPixelColor(i, ring.Color(0, 255, 0));
      ring.show();
      delay(500);
    }    
  }
}