SOURCE

function setup() {
    createCanvas(500, 500);
    noStroke();
    colorMode(HSB,360,150,150);
    }
function draw(){
    for(let x=20; x<width; x+=30){
        for(let y=20; y<height; y+=30){
            fill(55,255,210);
         ellipse(x,y,30,30);
    }
  }
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.1.9/p5.min.js"></script>