odoo中的看板颜色及拖动追加

看板中有个分组，我要实现的效果是拖动任务到一个分组，这个分组的颜色都为一个色，kanban默认的颜色是鼠标点击改变，我要实现的效果是拖动到某个分组，看板背景色自动设置为这个分组的颜色。并且把拖动经过的分组追加到一个字符串，这个字符串显示在看板上，可以看见那些是已经拖动过的。
上代码

完成进度：
  


    color = fields.Integer('Color Index',compute='_compute_color')
    priority = fields.Selection([('0', 'Low'), ('1', 'Normal'), ('2', 'High')], 'Priority', default='1')
    kanban_state = fields.Selection(
        [('normal', '进行中'), ('blocked', '阻塞'), ('done', '已完成')], 'Kanban State',
        default='normal')
    stage_id = fields.Many2one('loan.record.stage', u'阶段', group_expand='_read_group_stage_ids', default=1,track_visibility='onchange')

 @api.onchange('stage_id')
    def _compute_color(self):
        for x in self:
            x.color = x.stage_id.id
    @api.multi
    def write(self,vals):
        probability_o = self.probability
        if vals.has_key('stage_id'):
            probability = self.stage_id.name
            if probability_o==False:
                vals['probability']=str(probability)
            else:
                vals['probability'] = str(probability_o) + '->' + str(probability)
        if vals and 'kanban_state' not in vals and 'stage_id' in vals:
            vals['kanban_state'] = 'normal'
        return super(LoanRecord, self).write(vals)