Arduino UNO

const int redPin = 11;
const int greenPin = 10;
const int bluePin = 9;
void setup() {
 // Start off with the LED off.
 setColourRgb(0,0,0);
}
void loop() {
 unsigned int rgbColour[3];
 // Start off with red.
 rgbColour[0] = 255;
 rgbColour[1] = 0;
 rgbColour[2] = 0;  
 // Choose the colours to increment and decrement.
 for (int decColour = 0; decColour < 3; decColour += 1) {
   int incColour = decColour == 2 ? 0 : decColour + 1;
   // cross-fade the two colours.
   for(int i = 0; i < 255; i += 1) {
     rgbColour[decColour] -= 1;
     rgbColour[incColour] += 1;
     setColourRgb(rgbColour[0], rgbColour[1], rgbColour[2]);
     delay(5);
   }
 }
}
void setColourRgb(unsigned int red, unsigned int green, unsigned int blue) {
 analogWrite(redPin, red);
 analogWrite(greenPin, green);
 analogWrite(bluePin, blue);
}