float[] red = new float[255];
float[] green = new float[255];
float[] blue = new float[255];

void setup () {
  size(200, 200);
  background(255);
  noStroke();
  rectMode(CENTER);
  frameRate(5);
}

void draw() {

   for(int i = 0; i < 255; i++) {
     red[i] = random(255);
     green[i] = random(255);
     blue[i] = random(255);    
     fill(red[i], green[i], blue[i]);
     background(100 + (sin(red[i])*200));
     rect(55, 55, 70, 70);
    }
    for(int j = 0; j < 255; j++) {
      red[j] = random(255);
      green[j] = random(255);
      blue[j] = random(255);    
      fill(red[j], green[j], blue[j]);
      rect(145, 55, 70, 70);
    }
    for(int k = 0; k < 255; k++) {
      red[k] = random(255);
      green[k] = random(255);
      blue[k] = random(255);    
      fill(red[k], green[k], blue[k]);
      rect(55, 145, 70, 70);
    }
    for(int l = 0; l < 255; l++) {
      red[l] = random(255);
      green[l] = random(255);
      blue[l] = random(255);    
      fill(red[l], green[l], blue[l]);
      rect(145, 145, 70, 70);
    }  

}