How do I fix this Menu in CSS?

On this site;
http://nickprowse.com

One the sub-menu on the Navigation at the left, when you press + and the sub-menu drops down, there is a darker green background, how do I remove that please?

I managed to change the line height but couldn't change background colour, e.g.;

/* --Custom CSS--
================================================*/

.navigation ul a {
line-height: 70%; padding: 0px !important;
}

.lv2-menu{
position:relative; line-height: 70%; padding: 0px !important;
}

/* --Navigation--
Here is the Main CSS file;
================================================*/

.navigation {
margin-top: 25.026%;
}

.lv2-menu{
position:relative;
}

.lv2-menu:before{
content:"";
position:Absolute;
top:17px;
right:8px;
width:2px;
height:8px;
background-color:#fff;
}

.lv2-menu:after{
content:"";
position:absolute;
top:20px;
right:5px;
width:8px;
height:2px;
background-color:#fff;
}

.show-sub:before{
display:none;
}

.navigation a {
font-weight:Bold;
letter-spacing:0px;
line-height:12px;
padding:15px 0;
display:block;
}

.navigation ul{
display:none;
}

.navigation ul a{
position:relative;
padding:10px;
margin:5px 0;
background-color:rgba(0,0,0,0);
}

.navigation ul a:hover{
background-color:rgba(0,0,0,0.1);
}

.navigation > li:first-child > a{
border-top:none;
}

.navigation > li:last-child > a{
border-bottom:none;
}

.navigation > li > a:hover,.navigation > .current_page_item > a{
text-shadow: 0px 0px 10px #FFFFFF;
}