A canvas strokeStyle example

function canvasReady() {
  draw(document.getElementById('canvas').getContext('2d'));
}
function draw(ctx) {
  var i, j;
  for (i=0;i<6;i++){
    for (j=0;j<6;j++){
      ctx.strokeStyle = 'rgb(0,' + Math.floor(255-42.5*i) + ',' + 
                       Math.floor(255-42.5*j) + ')';
      ctx.beginPath();
      ctx.arc(12.5+j*25,12.5+i*25,10,0,Math.PI*2,true);
      ctx.stroke();
    }
  }
}