checkbox/ radoi默认不支持更改背景颜色，这里可以使用伪类来实现。基本原理是利用after/ before插入新的元素。而后利用新元素的背景颜色或者背景图片覆盖掉原来的样式。

CSS代码：

input[type=checkbox] {
 margin-right: 5px;
 cursor: pointer;
 font-size: 14px;
 width: 15px;
 height: 12px;
 position: relative;
}
input[type=checkbox]:after {
 position: absolute;
 width: 10px;
 height: 15px;
 top: 0;
 content: " ";
 background-color: #ff0000;
 color: #fff;
 display: inline-block;
 visibility: visible;
 padding: 0px 3px;
 border-radius: 3px;
}
input[type=checkbox]:checked:after {
 content: "?";
 font-size: 12px;
}
input[type=radio] {
 margin-right: 5px;
 cursor: pointer;
 font-size: 14px;
 width: 15px;
 height: 12px;
 position: relative;
}
input[type=radio]:after {
 position: absolute;
 width: 10px;
 height: 15px;
 top: 0;
 content: " ";
 background-color: #ff0000;
 color: #fff;
 display: inline-block;
 visibility: visible;
 padding: 0px 3px;
 border-radius: 50%;
}
input[type=radio]:checked:before {
 content: "?";
 display: block;
 position: relative;
 top: -2px;
 left: 3px;
 width: 6px;
 height: 6px;
 color: #fff;
 font-weight: 400;
 z-index: 1;
}

HTML 示例：

plus

minus

plus

minus

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