To Generate above pattern.
Note : change translate parameter to get different result that is the difference between  this and previous one

float r = 0;

void setup() {
  size(400,400);
  background(10);
  smooth();
  noStroke();
}
void draw() {
  //translate(width/2, height/2);
  fill(255);
  rotate(r);
  float circle_size = random(5, 15);
  fill(0,random(r,255),random(r,255));
  ellipse(100 + r, 10, circle_size, circle_size);
  r = r + 0.2;
  println(r);
  if(r>150)
    r=0;
}

Simple Processing Generative Art/Drawing 3

To Generate Above drawing
Note : Play with fill to get different color

float r = 0;

void setup() {
  size(400,400);
  background(10);
  smooth();
  noStroke();
}
void draw() {
  translate(width/2, height/2);
  fill(255);
  rotate(r);
  float circle_size = random(5, 15);
  fill(0,random(r,255),random(r,255));
  ellipse(100 + r, 10, circle_size, circle_size);
  r = r + 0.2;
  println(r);
  if(r>150)
    r=0;
}

Simple Processing Generative Art/Drawing 2

Code to generate above patten

1. For rectangle

void setup(){
size(600,600);
}

void draw(){
noStroke();
fill(random(255),random(255),random(255),random(255));
rect(random(255),random(255),random(255),random(255));
}

2. For Ellipse

void setup(){
size(600,600);
}

void draw(){
noStroke();
fill(random(255),random(255),random(255),random(255));
ellipse(random(255),random(255),random(255),random(255));
}

Simple Processing Generative Art/Drawing 1

Code to generate above pttern

void setup(){

    size(255,255);

}

void draw(){

    float r=random(255);

    float b=random(255);

    float g=random(255);

    stroke(r,b,g);

    line(0,0,r,b);

}