What Printable Element Is Better To Use Than Linear-gradient?

I have this DnD application where i use CSS 'linear-gradient' to show the user where a blind spot is. It looks like this: https://jsfiddle.net/y03q0zmn/1/

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    <table>
      <tr>
        <td colspan="3"> This is main heading</td>
      </tr>
      <tr>
        <td width="50px">LEFT1</td>
        <td width="50px">Middle1</td>
        <td width="50px">RIGHT1</td>
      </tr>
       <tr>
        <td width="50px">LEFT2</td>
        <td width="50px">Middle2</td>
        <td width="50px">RIGHT2</td>
      </tr>
    </table>