size(800, 250);
smooth();
background(255);
noStroke();

int i = 0;
while (i <= width) {
  fill(0, random(255), random(50, 100), 50);
  float s = 80 + random(40);
  ellipse(i, height/2, 70, 70);
  ellipse(i, height/2, s, s);
  i = i + 40;
}