Hide Content color! or hidden content color cuz you have used [hide][/hide] tags if so then
Goto your Theme section choose the theme and click on Edit HTML AND CSS
after that find the template bim_hide_box and you will some code written in it, just copy the below code and overwrite it and save
<!--startHideContent-->
<div id="bimHiddenBoxLine">
<div id="bimHiddenBox" class="bimHiddenBox ipsMessage ipsMessage_success">
<!-- <strong>{lang="bim_hide_title"}</strong> -->
{lang="bim_hide_title"}
</div>
<ul class='ipsList_inline'>
{$content|raw}
</ul>
</div>
<!--endHideContent-->
now after that goto you css tab and find bimhidecontent.css then open it and again you'll see some code in it, just copy the code below and paste (overwrite)
.bimHiddenBox {
background: #212327 !important; /* choose your color, its in hex */
/*border: 1px solid #212327;*/
/*color: #000 !important;*/
}
#bimHiddenBoxLine{
border: 2px solid #212327; /* choose your color, its in hex */
}
Enjoy