加入以下样式
html{
filter: grayscale(100%);
-webkit-filter: grayscale(100%);
-moz-filter: grayscale(100%);
-ms-filter: grayscale(100%);
-o-filter: grayscale(100%);
filter: progid:DXImageTransform.Microsoft.BasicImage(grayscale=1);
-webkit-filter: grayscale(1);
}