int RED = 11;   //Connect red color leg of RGB to PWM digital pin 11
int GREEN = 10; //Connect green color leg of RGB to PWM digital pin 10
int BLUE = 9;  //Connect blue color leg of RGB to PWM digital pin 9

void setup() {
   RGBcolor(0,0,0);
   pinMode(RED, OUTPUT); // Set RED pin as an output pin
  pinMode(GREEN, OUTPUT); // Set GREEN pin as an output pin
  pinMode(BLUE, OUTPUT); // Set BLUE pin as an output pin
  Serial.begin(9600);
 
}

void loop() {

    if(Serial.available() > 0){
     char Mycolor = Serial.read();
           if(Mycolor == 'r'){
             RGBcolor(255,0,0);
           }

        else if (Mycolor == 'g'){
           RGBcolor(0,255,0);
        }
         else if (Mycolor == 'b'){
           RGBcolor(0,0,255);
        }

          else if (Mycolor == 'd'){
           RGBcolor(random(0,255),random(0,255),random(0,255));
        }

         else {
          RGBcolor(0,0,0);
          
         }
      }

}

void RGBcolor(int Rval, int Gval, int Bval){

  Rval = 255-Rval;
  Gval = 255-Gval;
  Bval = 255-Bval;
  analogWrite(RED,Rval);
  analogWrite(GREEN,Gval);
  analogWrite(BLUE,Bval);

}