:in-range {
  /* ... */
}

<form action="" id="form1">
  <ul>
    Values between 1 and 10 are valid.
    <li>
      <input
        id="value1"
        name="value1"
        type="number"
        placeholder="1 to 10"
        min="1"
        max="10"
        value="12"
        required />
      <label for="value1">Your value is </label>
    </li>
  </ul>
</form>

li {
  list-style: none;
  margin-bottom: 1em;
}

input {
  border: 1px solid black;
}

input:in-range {
  background-color: rgba(0, 255, 0, 0.25);
}

input:out-of-range {
  background-color: rgba(255, 0, 0, 0.25);
  border: 2px solid red;
}

input:in-range + label::after {
  content: "okay.";
}

input:out-of-range + label::after {
  content: "out of range!";
}