// Define variables:
/*
  byte ledG=5;
  byte ledR=3;
  byte ledB=6;
*/

byte current[3]={255,255,255};

void setup(){
  pinMode(3, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  // Make random seed to generate colours:
  randomSeed(analogRead(0));
}

void loop(){
  // Assign values to each color
  byte newR=(byte) random() % 255;
  byte newG=(byte) random() % 255;
  byte newB=(byte) random() % 255;

  while(current[0] != newR || current[1] != newG || current[2] != newB){
      current[0]=adjust(current[0], newR, 3);
      current[1]=adjust(current[1], newG, 5);
      current[2]=adjust(current[2], newB, 6);
  }
  /* more efficient but
  /* while(current[0] != newR){ */
  /*     current[0]=adjust(current[0], newR, 3); */
  /* } */
  /* while(current[1] != newG){ */
  /*     current[1]=adjust(current[1], newG, 5); */
  /* } */
  /* while(current[2] != newB){ */
  /*     current[2]=adjust(current[2], newB, 6); */
  /* } */
  delay(180000);
}

byte adjust(byte oldVal, byte newVal, byte pinNo){
    if(oldVal > newVal){
        analogWrite(pinNo, oldVal-1);
        return oldVal-1;
    }else if(oldVal < newVal){
        analogWrite(pinNo, oldVal+1);
        return oldVal+1;
    }else{
        return oldVal;
    }
}