Cell border lost when trying to add cell data <td>

Hi,
When I try to add 'dotgreen'as cell data to my table, the cell border disappears. What am i doing wrong? Please help!

Here is the HTML scrap:
 <tr>
             <td>Customisable modular interiors</td>
             <td class="dotorange"></td>   
             <td></td>
             <td></td>
             <td></td>
             <td></td>
             <td class="dotred"></td>   
       </tr> 

Here is the CSS dotgreen property:
.dotgreen{
  height: 2px;
  width: 2px;
  margin-left: 20%;
  margin-right: auto;
  background-color: green;
  border-radius: 50%;
  display: inline-block;
}