Simple little arduino sketch that cycles through a bunch of color combinations on an arduino driving an RGB LED.

rgb_cycle

const int RED_PIN = 9;
const int GREEN_PIN = 10;
const int BLUE_PIN = 11;
const int MAX_VAL=255;



void setup() {
  // initialize digital pins as output: 
  for (int i = PIN_BASE; i <= PIN_BASE+PIN_CT; i++) {
    pinMode(i, OUTPUT);
  }  
  // Start off with the LED .  (0 = 
   setColorRgb(RED_PIN,0, GREEN_PIN,0, BLUE_PIN,0);
}

const bool INVERT=true;  // invert if driving a common anode RBG LED
void setColorRgb(unsigned int redPin, unsigned int red, unsigned int greenPin, unsigned int green, unsigned int bluePin, unsigned int blue) {
  analogWrite(redPin, INVERT? 255-red: red);
  analogWrite(greenPin, INVERT? 255-green: green);
  analogWrite(bluePin, INVERT? 255-blue: blue);
}
 
void fader(
    int r_pin, int r_start, int r_end,
    int g_pin, int g_start, int g_end,
    int b_pin, int b_start, int b_end)
{    
  int steps=16;
  int one_step=MAX_VAL/steps;
  int delay_ms=20;

  int r_delta = (r_end - r_start)/steps;
  int g_delta = (g_end - g_start)/steps;
  int b_delta = (b_end - b_start)/steps;
  
  int r_now = r_start;
  int g_now = g_start;
  int b_now = b_start;

  int i=0; 
  setColorRgb(r_pin, r_now, g_pin, g_now, b_pin, b_now);
  while (i < MAX_VAL) {
    r_now += r_delta;
    g_now += g_delta;
    b_now += b_delta;
    setColorRgb(r_pin, r_now, g_pin, g_now, b_pin, b_now);
    delay(delay_ms);
    i += one_step;
  }
}  

void loop() {
  // white
  fader(RED_PIN,0,MAX_VAL, GREEN_PIN,0,MAX_VAL, BLUE_PIN,0,MAX_VAL);
  delay(100); 
  fader(RED_PIN,MAX_VAL,0, GREEN_PIN,MAX_VAL,0, BLUE_PIN,MAX_VAL,0);
  delay(100); 


  //red
  fader(RED_PIN,0,MAX_VAL, GREEN_PIN,0,0, BLUE_PIN,0,0);
  delay(100); 
  fader(RED_PIN,MAX_VAL,0, GREEN_PIN,0,0, BLUE_PIN,0,0);
  delay(100); 
  //green
  fader(RED_PIN,0,0, GREEN_PIN,0,MAX_VAL, BLUE_PIN,0,0);
  delay(100); 
  fader(RED_PIN,0,0, GREEN_PIN,MAX_VAL,0, BLUE_PIN,0,0);
  delay(100); 
  //blue
  fader(RED_PIN,0,0, GREEN_PIN,0,0, BLUE_PIN,0,MAX_VAL);
  delay(100); 
  fader(RED_PIN,0,0, GREEN_PIN,0,0, BLUE_PIN,MAX_VAL,0);
  delay(100);

  //redless (cyan)
  fader(RED_PIN,0,0, GREEN_PIN,0,MAX_VAL, BLUE_PIN,0,MAX_VAL);
  delay(100); 
  fader(RED_PIN,0,0, GREEN_PIN,MAX_VAL,0, BLUE_PIN,MAX_VAL,0);
  delay(100);
  
  //blueless yellow
  fader(RED_PIN,0,MAX_VAL, GREEN_PIN,0,MAX_VAL, BLUE_PIN,0,0);
  delay(100); 
  fader(RED_PIN,MAX_VAL,0, GREEN_PIN,MAX_VAL,0, BLUE_PIN,0,0);
  delay(100); 

  // greenless magenta
  fader(RED_PIN,0,MAX_VAL, GREEN_PIN,0,0, BLUE_PIN,0,MAX_VAL);
  delay(100); 
  fader(RED_PIN,MAX_VAL,0, GREEN_PIN,0,0, BLUE_PIN,MAX_VAL,0);
  delay(100); 


  fader(RED_PIN,0,MAX_VAL, GREEN_PIN,0,0, BLUE_PIN,0,0);
  delay(100); 
  fader(RED_PIN,MAX_VAL,0, GREEN_PIN,0,MAX_VAL, BLUE_PIN,0,0);
  delay(100); 
  fader(RED_PIN,0,0, GREEN_PIN,MAX_VAL,0, BLUE_PIN,0,MAX_VAL);
  delay(100); 
  fader(RED_PIN,0,MAX_VAL, GREEN_PIN,0,0, BLUE_PIN,MAX_VAL,0);
  delay(100); 
  fader(RED_PIN,MAX_VAL,0, GREEN_PIN,0,MAX_VAL, BLUE_PIN,0,0);
  delay(100); 
  fader(RED_PIN,0,0, GREEN_PIN,MAX_VAL,0, BLUE_PIN,0,MAX_VAL);
  delay(100); 
  fader(RED_PIN,0,MAX_VAL, GREEN_PIN,0,0, BLUE_PIN,MAX_VAL,0);
  fader(RED_PIN,MAX_VAL,0, GREEN_PIN,0,0, BLUE_PIN,MAX_VAL,0);
  delay(1000); 
 
}