Return color for a verb.  verbs - Top verbs, order of which determines color verb  - The verb you're looking to color  Returns color suitable for styling an element (rgba).
function verbColor(verbs, verb) {
    var index = verbs.indexOf(verb),
        color = (index >= 0) ? VERB_COLORS(index) : "#ccc",
        rgb = d3.rgb(color);
    return "rgba(" + rgb.r + "," + rgb.g + "," + rgb.b + ",0.5)"
  }