A simple test of interpolateHcl from the d3-color module, animated with timer from the d3-transition module. Note that interpolateHcl chooses the shortest path between two hues, and the change in hue is thus always less than 180°; use interpolateHclLong to take the long path.
xxxxxxxxxx<meta charset="utf-8"><canvas width="960" height="1" style="width:960px;height:500px;"></canvas><script src="d3.min.js"></script><script>var canvas = document.querySelector("canvas"), width = canvas.width, context = canvas.getContext("2d"), image = context.createImageData(width, 1);d3.timer(function(elapsed) { var hue = elapsed * .1, interpolate = d3.interpolateHcl(d3.hcl(hue, 50, 95), d3.hcl(hue + 120, 50, 25)); for (var i = 0, j = -1, c; i < width; ++i) { c = d3.rgb(interpolate(i / (width - 1))); image.data[++j] = c.r; image.data[++j] = c.g; image.data[++j] = c.b; image.data[++j] = 255; } context.putImageData(image, 0, 0);});</script>