Hopefully you could translate my instructions properly.
Under bb_plugins.php, paste this code:
if($user_id==1){
$colorPickerBtn=<<<out
<a href="JavaScript:doPicker()" onmouseover="window.status='{$l_bb_color}'; return true" onmouseout="window.status=''; return true" onmousemove="pasteSel()"><img src="https://www.minibb.com/forums/img/button_color.gif" style="width:22px;height:22px" alt="{$l_bb_color}" title="{$l_bb_color}" /></a>
out;
}
then instead of the code the add-on provides, paste into templates/main_post_form.ht
ml:
{$colorPickerBtn}
You should leave the code between
<!-- BEGIN COLOR PICK -->
...
<!-- END COLOR PICK -->
as it's provided in README.
That's a simple logics...