css样式 style="filter:grayscale(100%)"
在style.css的body中加入即可：
body, h1, h2, h3, h4, h5, h6, hr, blockquote, dl, p, dt, dd, ul, ol, li, pre, form, fieldset, lengend, button, input, textarea, th, td {
margin: 0;
padding: 0;
filter:grayscale(100%)
}