How to make chosen options in a form change colour

So I have an html code like this

`<center><form action=" " method="get"> <input style="display:inline" type="hidden" name="srtby" value="updated"> <input style="display:inline" type="hidden" name="srtdir" value="desc"> <input style="display:inline" type="hidden" name="__filelist_page" value="1"><img src="/i/i5/fs.png" alt=""><input style="border:1px solid
#ffffff;border-radius:2px;background:#3b5998;color:#ffffff;padding:0 1px !important;margin: 1px !important;font-size:.75em;text-decoration:none !important;width:5em" type="search" name="fltr" value=""><input style="border:1px solid
#ffffff;border-radius:2px;background:#3b5998;color:#ffffff;padding:0 1px !important;margin: 1px !important;font-size:.75em;text-decoration:none !important" type="submit" value="Search"> <br><a style="border:1px solid
#ffffff;border-radius:2px;background:#3b5998;color:#ffffff;padding:0 1px !important;margin: 1px !important;font-size:.75em;text-decoration:none !important;color:#0f0 !important" href="?srtby=updated&amp;srtdir={_$srtdir|}&amp;fltr=&amp;prpg=10&amp;__filelist_page=1" title="Updated"><b>Updated</b></a> . <a style="border:1px solid
#ffffff;border-radius:2px;background:#3b5998;color:#ffffff;padding:0 1px !important;margin: 1px !important;font-size:.75em;text-decoration:none !important;" href="?srtby=name&amp;srtdir={_$srtdir|}&amp;fltr=&amp;prpg=10&amp;__filelist_page=1" title="Name"><b>Name</b></a> . <a style="border:1px solid
#ffffff;border-radius:2px;background:#3b5998;color:#ffffff;padding:0 1px !important;margin: 1px !important;font-size:.75em;text-decoration:none !important;" href="?srtby=size&amp;srtdir={_$srtdir|}&amp;fltr=&amp;prpg=10&amp;__filelist_page=1" title="Size"><b>Size</b></a> . <a style="border:1px solid
#ffffff;border-radius:2px;background:#3b5998;color:#ffffff;padding:0 1px !important;margin: 1px !important;font-size:.75em;text-decoration:none !important;" href="?srtby=type&amp;srtdir={_$srtdir|}&amp;fltr=&amp;prpg=10&amp;__filelist_page=1" title="type"><b>Type</b></a><br><a style="border:1px solid
#ffffff;border-radius:2px;background:#3b5998;color:#ffffff;padding:0 1px !important;margin: 1px !important;font-size:.75em;text-decoration:none !important;" href="?srtby={_$srtby|}&amp;srtdir=asc&amp;fltr=&amp;prpg=10&amp;__filelist_page=1" title="Ascending"><b>Ascending</b></a> . <a style="border:1px solid
#ffffff;border-radius:2px;background:#3b5998;color:#ffffff;padding:0 1px !important;margin: 1px !important;font-size:.75em;text-decoration:none !important;color:#0f0 !important" href="?srtby={_$srtby|}&amp;srtdir=desc&amp;fltr=&amp;prpg=10&amp;__filelist_page=1" title="Descending"><b>Descending</b></a> <br><select style="border:1px solid
#ffffff;border-radius:2px;background:#3b5998;color:#ffffff;padding:0 1px !important;margin: 1px !important;font-size:.75em;text-decoration:none !important;" name="prpg"> <option>3</option> <option>5</option> <option selected="selected" class="selected">10</option> <option>20</option> <option>50</option> <option value=" ">all</option> </select><input style="border:1px solid
#ffffff;border-radius:2px;background:#3b5998;color:#ffffff;padding:0 1px !important;margin: 1px !important;font-size:.75em;text-decoration:none !important" type="submit" value="Per Page"></form></center>`

All I want is for the chosen options in the chosen options to change colour