rainbowarduino.cpp

#include <Adafruit_NeoPixel.h>
#ifdef __AVR__
  #include <avr/power.h>
#endif
#define NEOPIXEL_COUNT 4
#define NEOPIXEL_PIN 4
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NEOPIXEL_COUNT, NEOPIXEL_PIN, NEO_GRB + NEO_KHZ800);
unsigned int rgbColor[] {255, 0, 0};
int decColor = 0;
  
void setup() {
  pixels.begin(); // This initializes the NeoPixel library.
}

void loop() {
  if (rgbColor[decColor] == 0) {
    decColor++;
    if (decColor == 3) decColor=0;
  }
  int incColor = decColor == 2 ? 0 : decColor + 1;
  rgbColor[decColor] -= 1;
  rgbColor[incColor] += 1;
  for (uint8_t u = 0; u < NEOPIXEL_COUNT; u++)
    {
          pixels.setPixelColor(u, pixels.Color(rgbColor[0], rgbColor[1], rgbColor[2])); // Moderately bright green color.
    }
    pixels.show();
    delay(5);
}