#include <Adafruit_NeoPixel.h>

#define PIN       12
#define NUMPIXELS 16
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

const int l[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() {
  // put your main code here, to run repeatedly:
  for (int j = 0; j < 16; j++) {
    for (int i = 0; i < 16; i++)
      if (i <= j)
        pixels.setPixelColor(i, l[cnt][0], l[cnt][1], l[cnt][2]);
      else
        pixels.setPixelColor(i, 0, 0, 0);

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