It's pretty amazing to me that in 2018, the way we pass colors to a modern graphics API is to build a string with comma separated list of the individual components encoded in decimal.

And then people wonder why computers feel slower than they did 15 years ago.

Legacy APIs for DOM are hard to get rid of, which the Canvas API is based on. There is some progress though: https://developers.google.com/web/updates/2018/03/cssom

You can save this as an HTML file:

  <canvas id="canvas" width="400" height="400"></canvas>

  <script>
  var canvas = document.getElementById('canvas');
  var ctx = canvas.getContext('2d');
  var width = canvas.width;
  var height = canvas.height;
  var imagedata = ctx.createImageData(width, height);

  function draw(r, g, b, x, y){
    var pixelindex = (y * width + x) * 4;
    imagedata.data[pixelindex] = r;
    imagedata.data[pixelindex+1] = g;
    imagedata.data[pixelindex+2] = b;
    imagedata.data[pixelindex+3] = 255; //alpha
    ctx.putImageData(imagedata, 0, 0);
  }

  </script>

This gives you a 400x400 space to draw on. Open the console and call draw().

  draw(0,0,0,15,15);

LOL, not even close.