SOURCE

let c=[];
function setup(){
    createCanvas(480,480);
    background(0);
    for(let i=0;i<1728;i++){
        c[i]=random(255);
    }
}
function draw(){
    let cIndex=0;
    for(let x=0;x<480;x+=22){
        for(let y=0;y<480;y+=22){
            fill(c[cIndex],c[cIndex+1],c[cIndex+=3]);
            ellipse(x,y,20,20);
            cIndex+=1;

        }
    }
}

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