var domain = ["poor", "good", "great"];
var ordinalScale = d3.scaleOrdinal()
  .domain(domain)
  .range(["blue", "white", "red"]);

// Arrow functions: Chrome 45, FF 22, Edge, Opera 32, Safari 10. No IE.
domain.forEach(grade => {
  console.log(grade, ordinalScale(grade));
});