#include <Adafruit_NeoPixel.h>
#define pin 12
#define NUMPIXELS 16
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, pin, NEO_GRB + NEO_KHZ800);
int color[3][3] ={{255,0,0},{0,255,0},{0,0,255}};
void setup() {
  // put your setup code here, to run once:
  pixels.begin();
}

int cnt=0;

void loop() {

  for (int j = 15; j > -1; j--) {

    for (int i = 0; i < 16; i++) {
      if (i>=j) 
        pixels.setPixelColor(i, color[cnt][0],color[cnt][1],color[cnt][2]);
      else 
        pixels.setPixelColor(i, 0, 0, 0);
    }

    pixels.show();
    delay(100);
  }
  if (++cnt>2) {
    cnt=0;
  }
}