<form>
  <input type="text" value="有効フォーム">
  <input type="button" value="決定">
</form>
<form>
  <input type="text" value="無効フォーム" disabled="disabled">
  <input type="button" value="決定" disabled="disabled">
</form>
input:enabled{
  color: #ff0000;
}
input:disabled{
  color: #0000ff;
}

External CSS

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External JavaScript

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