gistfile1.txt

import processing.serial.*;

Serial myPort;        // The serial port

float valorArduinoA = 0;
float valorArduinoB = 0;

String valoresArduino[];

long prevTimeColorChanges = 0;

boolean isRed = true;

void setup () {
  size(800, 300);  
  smooth();
  noStroke();
  background(255);
  serialSetup();
}

void draw () {
  background(255);

  long currenTime = millis();

  if (valorArduinoB > 20 && (currenTime - prevTimeColorChanges) > 1000) {
    if (isRed) {
      isRed = false;
      fill(0, 0, 255);
    } 
    else {
      isRed = true;
      fill(255, 0, 0);
    }
  } 

  float diameter = map(valorArduinoA, 840, 940, height/2, height-10);
  ellipse(width/2, height/2, diameter, diameter);
}


void serialSetup() {
  println(Serial.list());
  myPort = new Serial(this, Serial.list()[5], 9600);
  myPort.bufferUntil('\n');
}

void serialEvent (Serial myPort) {
  String lineaArduino = myPort.readStringUntil('\n'); 

  if (lineaArduino != null) {
    lineaArduino = trim(lineaArduino); 
    valoresArduino = split(lineaArduino, ","); 
    valorArduinoA = float(valoresArduino[0]);
    valorArduinoB = float(valoresArduino[1]);

  }
}

More processing Arduino examples: https://github.com/fablabbcn/Workshops/tree/master/Talking%20with%20processing