#include <Adafruit_NeoPixel.h>

#define PIN        D3     // Change this pin to the one you're using for DIN
#define NUMPIXELS 8      // Change this based on how many LEDs you have

Adafruit_NeoPixel pixels(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  Serial.begin(9600);
  pixels.begin();
  pixels.clear();
  pixels.show();
}

void loop() {
  if (Serial.available()) {
    char c = Serial.read();
    uint32_t color;

    switch (c) {
      case 'r':
        color = pixels.Color(255, 0, 0); // red
        break;
      case 'b':
        color = pixels.Color(0, 0, 255); // blue
        break;
      case 'y':
        color = pixels.Color(255, 255, 0); // yellow
        break;
      case 'x': // random
        color = pixels.Color(random(0, 255), random(0, 255), random(0, 255));
        break;
      default:
        return;
    }

    for (int i = 0; i < NUMPIXELS; i++) {
      pixels.setPixelColor(i, color);
    }
    pixels.show();
  }
}