Specifying arcs with different colors in Datamaps.js

paths.js

var paths = [
  {
    "origin":{"latitude":42.350939,"longitude":-71.05229},
    "destination":{"latitude":35.466872,"longitude":139.622747},
    "options": {"strokeWidth": 2, "strokeColor": "rgba(0,0,255,0.33)"}
  },
  {
    "origin":{"latitude":42.350939,"longitude":-71.05229},
    "destination":{"latitude":39.908617,"longitude":19.581969},
    "options": {"strokeWidth": 1, "strokeColor": "rgba(0,0,255,0.33)"}
  }
  ...
];

// http://datamaps.github.io

Hm, that's a fair point.
As for using the fillKey, ah, I hadn't thought to define the arc widths that way! I think that would be really spiffy!