checkbox选中背景颜色更改 

   input[type=checkbox] {
            cursor: pointer;
            position: relative;
            width: 18px;
            height: 18px;
            font-size: 12px;
        input[type=checkbox]::after {
            position: absolute;
            top: 0;
            color: #000;
            width: 18px;
            height: 18px;
            display: inline-block;
            visibility: visible;
            padding-left: 0px;
            text-align: center;
            content: ' ';
            border-radius: 3px
        input[type=checkbox]:checked::after {
            content: "✓";
            color: #fff;