<!DOCTYPE html>
<html>
<head>
<style>
#background {
background-color: yellow;
display: inline-block;
}
.container {
font-size: 0px;
}
</style>
</head>
<body>
<div id="background">
<div class="container">
<canvas id ="box-1" width="200" height="200"></canvas>
</div>
<div class="container">
<canvas id ="box-2" width="200" height="200"></canvas>
</div>
</div>
<script>
function drawCanvas(canvasID, color, width) {
var canvas = document.getElementById(canvasID);
var context = canvas.getContext("2d", {alpha: true});
context.clearRect(0, 0, canvas.width, canvas.height);
context.fillStyle = color;
context.fillRect(40, 40, width, width);
};
drawCanvas('box-1', 'rgb(50, 100, 150)', '50');
drawCanvas('box-2', 'rgb(150, 100, 50)', '100');
</script>
</body>
</html>