Simple fade up using different colors on an rgb led. Works by overflowing the unsigned char until it rolls over.

gistfile1.ino

/* Diyode CodeShield Pinout Constants */
#define ENCODER_A 14
#define ENCODER_B 15
#define ENCODER_PORT PINC
#define SWITCH 13
#define BUTTON 12
#define RGB_RED 11
#define RGB_GREEN 10
#define RGB_BLUE 9
#define LED 6
#define SERVO 5
#define PIEZO 3
#define RELAY 2
#define POT 2
#define HALL 3
#define THERMISTOR 4
#define PHOTOCELL 5

unsigned char redBrightness = 0;
unsigned char greenBrightness = round( 255 / 3.0f );
unsigned char blueBrightness = round( 255 / 3.0f ) * 2;

void setup () {
  pinMode( RGB_RED, OUTPUT );
  pinMode( RGB_GREEN, OUTPUT );
  pinMode( RGB_BLUE, OUTPUT );
}

void loop () {
  redBrightness ++;
  greenBrightness ++;
  blueBrightness ++;
  
  analogWrite( RGB_RED, redBrightness );
  analogWrite( RGB_GREEN, greenBrightness );
  analogWrite( RGB_BLUE, blueBrightness );
  
  delay (15);
}