SOURCE

let c=[];
function setup(){
createCanvas(480,400);
noStroke();
for(let i=0;i<80;i++){
    let x =random(width);
    let y =random(height);
c[i] = random(250);
}
}
function draw(){
background(120);
for(let i=0;i<24;i++){
    for(let j=0;j<24;j++){
        fill(c[j*24+24+i],[j*24+i+1],c[j*24+i+2]);
        ellipse(i*20,j*20,20,20);
    }
}
}

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