code: function() {
      this.appendDummyInput()
          .appendField('hue:')
          .appendField(new Blockly.FieldAngle('0', this.validator), 'HUE');
      this.setOutput(true, 'Colour');
      this.setTooltip('Paint the block with this colour.');
      this.setHelpUrl('https://www.youtube.com/watch?v=s2_xaEvcVI0#t=55');
    }
docs: Set the colour of the block.