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() {
   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
}

void loop() {
  
  RGBcolor(random(0,255),random(0,255),random(0,255)); //Call RGBcolor function
                                // which will send a random number between 0_255
                                //toeach color pin
  delay(1000);

}

void RGBcolor(int Rval, int Gval, int Bval){ //to give the desired value to each pin
  
  Rval = 255-Rval;//For common ANODE subtract the given number for RED from 255  
  Gval = 255-Gval;//For common ANODE subtract the given number for GREEN from 255  
  Bval = 255-Bval;//For common ANODE subtract the given number for BLUE from 255 
   
  analogWrite(RED,Rval); // Send modified RED color value to RED pin (PWM pin)
  analogWrite(GREEN,Gval);// Send modified GREEN color value to GREEN pin (PWM pin)
  analogWrite(BLUE,Bval);// Send modified BLUE color value to BLUE pin (PWM pin)
}