CSS有没有直接用class类名设置样式的方法？

比如有9个类名为son的元素 想给个别的元素设置样式是不是只能通过父级再用nth-of-type这些选择器设置？有没有直接给son设置的方法？

<div class="father">
   <div class="son">1</div>
   <div class="son">2</div>
   <div class="son">3</div>
   <div class="son">4</div>
   <div class="son">5</div>
   <div class="son">6</div>
   <div class="son">7</div>
   <div class="son">8</div>
   <div class="son">9</div>
</div>

用nth-child下面这样写无效

.items:nth-child(3) .items{
  background-color: #5ECE7E;
}
.items:nth-child(2) .items{
  background-color: #5DCDCB;
}

<div class="form relative">
        <div class="row1">
            <div class="items">
              <div class="grid-title">应收总额</div>
              <div class="grid-body" >
                <p> <span style="color: #488ff5">￥{{ billData.totalFee }}</span> <span class="grid-span">应收户数: {{billData.allNum}}</span></p>
              </div>
            </div>
            <div class="items">
              <div class="grid-title">逾期总额</div>
              <div class="grid-body">
                <p> <span style="color: #ef494e">￥{{ billData.delayFee }}</span> <span class="grid-span">逾期户数: {{billData.delayNum}}</span></p>
              </div>
            </div>
            <div class="items">
              <div class="grid-title">已收总额</div>
              <div class="grid-body">
                <p> <span style="color: #ef494e">￥{{ billData.collectedFee }}</span> <span class="grid-span">已收户数: {{billData.collectedNum}}</span></p>
              </div>
            </div>
</div>