SOURCE

let h=180
let u=90
function setup(){
    createCanvas(400,400);
    background(0);
   
  
   
}
function draw(){
    //background(0,30);
     strokeWeight(10);
    stroke(255);
    if(key=='A'){
        u-=5
    }
    if(key=='S'){
        u+=30
    }
    stroke(u,40,40);


    if(key=='Q'){
        h -=255 
    }
    if(key=='w'){
        h+=255
    }
    stroke(h,100,100);
    if(mouseIsPressed){
        line(mouseX,mouseY,pmouseX,pmouseY);
    }
}

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