var c;
function setup(){
   createCanvas(1800,1800);
   c=color(0,255,0);
}
function draw(){
   background(c);
   
   if (keyIsPressed){
     if (key=='r'){
        c=color(255,0,0);
     }
     if (key=='g'){
        c=color(0,255,0);
     }
     if (key=='b'){
        c=color(0,0,255);
     }