drop-shadow的屬性為： (x偏移, y偏移, 模糊大小, 色值)
CSS代碼

.icon {
    display: inline-block;
    width: 20px; height: 20px;
    overflow: hidden;
}
.icon-del {
    background: url(delete.png) no-repeat center;
}
.icon > .icon {
    position: relative;
    left: -20px;
    border-right: 20px solid transparent;
    -webkit-filter: drop-shadow(20px 0);
    filter: drop-shadow(20px 0);    
}

HTML代碼

<p><strong>原始圖標</strong></p>
<i class="icon icon-del"></i>
<p><strong>可以變色的圖標</strong></p>
<i class="icon"><i class="icon icon-del"></i></i>