After eight years, I faced the same challenge when trying to use the Stylish browser extension to change something on a website (not mine). And this time I made it work by looking at the source code using "inspect element" and created the CSS code based on that.
This it what it looked like before:
<table>_x000D_
<tbody>_x000D_
<tr>_x000D_
<td role="gridcell">_x000D_
<span title="In progress" style="background-color: #e2047a;color:White;margin:2px;border-radius:2px;padding-left: 2px; padding-right: 2px;text-align: center;width: 45px; display: block;overflow: hidden;text-overflow: ellipsis;">In progress</span>_x000D_
</td>_x000D_
</tr>_x000D_
</tbody>_x000D_
</table>
_x000D_
This is the same piece of the HTML and the CSS I used to modify the style:
td span[style="background-color: #e2047a;color:White;margin:2px;border-radius:2px;padding-left: 2px; padding-right: 2px;text-align: center;width: 45px; display: block;overflow: hidden;text-overflow: ellipsis;"] {_x000D_
width: 100px!important;_x000D_
}
_x000D_
<table>_x000D_
<tbody>_x000D_
<tr>_x000D_
<td role="gridcell">_x000D_
<span title="In progress" style="background-color: #e2047a;color:White;margin:2px;border-radius:2px;padding-left: 2px; padding-right: 2px;text-align: center;width: 45px; display: block;overflow: hidden;text-overflow: ellipsis;">In progress</span>_x000D_
</td>_x000D_
</tr>_x000D_
</tbody>_x000D_
</table>
_x000D_
You can run the code above and you will see that it works (tested in Chrome).
This is simply what I wanted back in the days when I asked this question.
I was using some sort of community blog/Myspace similar stuff and the only thing you had when styling your profile was their CSS editor, and that's why I wanted to select it based on the style.
I found the answer here: