I have a button whose original color is red and I want it to change its color when in focus to green using tab key and when you press enter the color should come back to red.

```
 <div style="position: absolute; margin: 0; left: 0; bottom: 0">
 <input class="button calculator large top-right-border   transition" type="submit" />
 </div>

 .button.calculator{
 background:red;
 }

.button.calculator:focus{
 background:green;
 }

```