Someone

char val;
int ledpin = 8;

void setup() {

  pinMode(ledpin, OUTPUT);
  Serial.begin(9600);

}

void loop() {

  if( Serial.available() )
  {
    val = Serial.read();
  }
  if( val == 'H' )
  {
    digitalWrite(ledpin, HIGH);
  } else { 
    digitalWrite(ledpin, LOW);
  }
  delay(100);

} 

import processing.serial.*;

Serial port;

color currentcolor;
RectButton rect1, rect2;
boolean locked = false;
void setup() {

  size(200, 200);
  color baseColor = color(102, 102, 102);
  currentcolor = baseColor;

  println(Serial.list()); 

  port = new Serial(this, Serial.list()[2], 9600);

  int x = 30;
  int y = 100;
  int size = 50;
  color buttoncolor = color(153, 102, 102);
  color highlight = color(102, 51, 51); 
  rect1 = new RectButton(x, y, size, buttoncolor, highlight);

  x = 90;
  y = 100; 
  size = 50;
  buttoncolor = color(153, 153, 153);
  highlight = color(102, 102, 102); 
  rect2 = new RectButton(x, y, size, buttoncolor, highlight);

}

void draw() {

  background(currentcolor);
  stroke(255);
  update(mouseX, mouseY);
  rect1.display();
  rect2.display();

}

void update(int x, int y) {

  if(locked == false) {

    rect1.update();
    rect2.update();
  } else {
    locked = false;
  }

  if(mousePressed) {
    if(rect1.pressed()) {
      currentcolor = rect1.basecolor;
      port.write('H');
    } else if(rect2.pressed()) {
      currentcolor = rect2.basecolor;
      port.write('L');
    }
  }

}

class Button {

  int x, y;
  int size;
  color basecolor, highlightcolor;
  color currentcolor;
  boolean over = false;
  boolean pressed = false;   

  void update() 
  {
    if(over()) {
      currentcolor = highlightcolor;
    } else {
      currentcolor = basecolor;
    }
  }

  boolean pressed() 
  {
    if(over) {
      locked = true;
      return true;
    } else {
      locked = false;
      return false;
    }    
  }

  boolean over() 
  { 
    return true; 
  }

  void display() 
  { 

  }

}

class RectButton extends Button {

  RectButton(int ix, int iy, int isize, color icolor, color ihighlight) 
  {
    x = ix;
    y = iy;
    size = isize;
    basecolor = icolor;
    highlightcolor = ihighlight;
    currentcolor = basecolor;
  }

  boolean over() 
  {
    if( overRect(x, y, size, size) ) {
      over = true;
      return true;
    } else {
      over = false;
      return false;
    }
  }

  void display() 
  {
    stroke(255);
    fill(currentcolor);
    rect(x, y, size, size);
  }

}

boolean overRect(int x, int y, int width, int height) {

  if (mouseX >= x && mouseX <= x+width && 
      mouseY >= y && mouseY <= y+height) {
    return true;
  } else {
    return false;
  }

}