SOURCE

let h=180;
let pointS=10;

function setup() {
createCanvas(500,500);
background(0);
colorMode(HSB,360,100,100);
}

function draw() {
strokeWeight(pointS);
stroke(h,100,100);
if(mouseIsPressed==true){
line(mouseX,mouseY,pmouseX,pmouseY);
}
if(keyIsPressed){
if((key=='q')||(key=='Q')){
h-=1;
}
if((key=='w')||(key=='W')){
h+=1;
}
}
if(keyIsPressed){
if((key=='a')||(key=='A')){
pointS-=0.5;
}
if((key=='s')||(key=='S')){
pointS+=0.5;
}
}

}

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