ColorScales.html

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title> Color Scales</title>
  <script src="https://d3js.org/d3.v4.js"></script>
  <script src="https://d3js.org/d3-selection-multi.v1.min.js"></script>
</head>
<body>
  <script>
        var data = d3.range(0, 20);
        var colorScale = d3.scaleOrdinal(d3.schemeCategory20);
        var svg = d3.select('body')
           .append('svg')
           .attrs({width: 400, height: 20});
        
        svg.selectAll('rect')
            .data(data)
            .enter()
            .append('rect')
            .attrs({
                fill: function(d) {
                    return colorScale(d);
                },
                x: function(d, i) {
                    return i * 20;
                },
                width: 20,
                height: 20
            });
      
  </script>
</body>
</html>