testing out chained transitions using d3.active
via d3 docs
d3.selectAll("circle").transition()
.delay(function(d, i) { return i * 50; })
.on("start", function repeat() {
d3.active(this)
.style("fill", "red")
.transition()
.style("fill", "green")
.transition()
.style("fill", "blue")
.transition()
.on("start", repeat);
});