SOURCE

let h=188;
let point=15;
function setup() {
createCanvas(400,400);
colorMode(HSB,360,100,100);
}

function draw() {
if(keyIsPressed){
    if(key=='s'){
    point-=1
    }
    else if(key=='a')
    point+=1
}
if(keyIsPressed){
if(key=='w'){
h-=1;
}
else if(key=='q'){
h+=1;
}
}
if(mouseIsPressed){
strokeWeight(point);
stroke(h,100,100);
line(mouseX,mouseY,pmouseX,pmouseY);
}
}

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