:read-write

/* 选择所有可编辑的 <input> 元素 */
/* Firefox 中需要加前缀 */
input:-moz-read-write {
  background-color: #bbf;
}

/* Supported in Blink/WebKit/Edge without a prefix */
input:read-write {
  background-color: #bbf;
}

<input type="text" value="Type whatever you want here.">
<input type="text" value="This is a read-only field." readonly>
<p>This is a normal paragraph.</p>
<p contenteditable="true">You can edit this paragraph!</p>

input { min-width: 25em; }
input:-moz-read-write { background: cyan; }
input:read-write { background: cyan; }

p:-moz-read-write { background: lightgray; }
p:read-write { background: lightgray; }
p[contenteditable="true"] { color: blue; }