Accept hexes as valid colors

[jmduke]

Currently the tool only accepts blue and green as valid arguments to color. The relevant code is in index.html:

function getColor(num, scale) {
  if(Config.color === 'blue') {
    // Index in the array is 1 less than the scaled_number
    return colorbrewer.Blues[scale][num - 1];
  }
  // Default to green
  else {
    return colorbrewer.Greens[scale][num - 1];
  }
}

Which is invoked in style():

color = getColor(feature.properties.scaled_value, Config.scale);